KIEV, Ukraine - The world rushed Thursday to help Ukraine, with the International Monetary Fund pledging up to $18 billion in loans, the U.N. condemning the vote that drove Crimea into Russian hands and the U.S. Congress backing even harsher sanctions against Russia.

Yet even with such intensive help to prop up the teetering economy, Ukraine’s prime minister warned of painful times ahead from economic changes that were sure to drive up energy prices.

In an address to parliament in Kiev, Prime Minister Arseniy Yatsenyuk warned that Ukraine was “on the brink of economic and financial bankruptcy” and laid out the fixes needed to put the country back on track.

“The time has come to tell the truth, to do difficult and unpopular things,” Yatsenyuk said, adding that Ukraine was short $25.8 billion - “equivalent to the entire state budget for this year.”

The IMF loan, which is expected to range between $14 billion and $18 billion, hinges on structural changes that Ukraine has pledged to undertake.

Ukraine’s new government finds itself caught between the demands of international creditors and a population that has endured decades of economic stagnation, corruption and mismanagement.

The changes demanded by the IMF - which include raising taxes, freezing the minimum wage and increasing energy prices - will hit households hard and are likely to strain the interim government’s tenuous hold on power.

One immediate change will be to let gas prices for households float up to become more in line with market prices. Ukraine for years has relied on discounted gas from Russia and then subsidized that further, so that residents are used to extremely low energy prices. Russia has abandoned the discounts and Ukraine’s government cannot afford the extra subsidy.

Other donors, including the European Union and Japan, have already pledged further aid to Ukraine, conditional on the IMF bailout package. The total amount of international assistance will be about $27 billion over the next two years.

Separately, the 28-nation EU has prepared a wider aid package including loans and grants for Ukraine expected to total more than $10 billion over the coming years.

President Barack Obama called the swell of international support a “concrete signal of how the world is united with Ukraine.”

“The decision to go forward with an IMF program is going to require a lot of courage,” Obama said, speaking in Rome. “It will require some tough decisions.”

CONGRESS RESPONDS

In Washington, Congress overwhelmingly backed legislation Thursday to aid Ukraine and punish Russia for its annexation of Crimea.

On a voice vote, the Senate approved a measure that would provide $1 billion in loan guarantees to Ukraine and give Obama broad authority to impose more sanctions on Russia and President Vladimir Putin’s inner circle. The names of senators participating in a voice vote are not recorded.

The House endorsed a different version on a 399-19 vote that also provides assistance to Ukraine and penalizes Russia. The four representatives from Arkansas, all Republicans, voted in favor of the House bill.

Lawmakers hope to send a single bill to the White House for Obama’s signature by week’s end.

Sen. Bob Menendez, D-N.J., chairman of the Senate Foreign Relations Committee, said the votes were “critical for President Putin to hear.”

“We are in a dangerous moment in history with global consequences and the world is watching,” he said.

Obama said in Rome that additional sanctions on Russia would inevitably also hit the economies of the U.S. and Europe. The U.S. and its allies are looking at Russia’s military, energy and finance industries as possible targets if it moves deeper into Ukraine, he said at a news conference.

“None of them, to have a powerful impact on Russia, are going to have zero impact on us because Russia is part of the world economy,” Obama said, appearing with Italian Prime Minister Matteo Renzi. “Everybody owns a piece of everything.”

Meanwhile, the U.N. General Assembly overwhelmingly affirmed Ukraine’s territorial integrity and deemed the referendum that led to Russia’s annexation of the Crimean Peninsula illegal.

The vote on the Ukraine-sponsored resolution in the 193-member world body was 100 countries in favor, 11 opposed and 58 abstentions. Twenty-four countries did not vote.

“This support has come from all corners of the world which shows that this [is] not only a regional matter but a global one,” Ukraine’s Foreign Minister Andriy Deshchytsia said after the vote.

He said the strong support reaffirms the U.N. Charter’s guarantee of territorial integrity and “will give an overwhelming majority of countries an additional argument” for “stronger and more concrete action” against Russia.

Russia’s U.N. Ambassador Vitaly Churkin had urged a “no” vote, saying a historic injustice in Crimea has been corrected and its people had expressed their right to self-determination in wanting to join Russia.

He called the resolution “confrontational in nature” and said it would be “counterproductive” to challenge the results of the referendum.

Russia shrugged off the torrent of criticism, announcing it would set up its own payment system to rival Visa and MasterCard after the two companies pulled their services from some Russian banks in the wake of international sanctions.

UKRAINE’S PLIGHT

Ukraine, a nation of 46 million, is battling to install a semblance of normalcy since President Viktor Yanukovych was ousted in February after months of protests ignited by his decision to back away from closer relations with the EU and turn toward Russia.

Over the past few weeks, an interim government has formed, Ukraine lost Crimea to Russia and further possible military incursions by Russia are feared.

After being voted in by lawmakers last month, Yatsenyuk described his task as a “kamikaze” mission, saying Ukraine is in a “great mess” with an empty treasury and foreign-currency reserves that have been “robbed.” Analysts have agreed, saying the interim government could pay a steep price.

“It is hard to explain to the voter that the worsening of the economy has happened not because of the revolution, but because of Viktor Yanukovych’s policies,” said Viktor Zamyatin of the Kiev-based Razumkov Center think tank.

One unpredictable source of potential unrest in Ukraine comes from the nationalist Right Sector movement, which rallied hundreds of protesters outside parliament Thursday in a demand for Interior Minister Arsen Avakov’s resignation after the killing this week of one of the group’s leaders. The group played a key role in toppling Yanukovych.

“The power is trying to rob our victory from us. But it is we that should be dictating terms, and we have the means to do this,” declared 31-year old Anton Turilo, who was wearing a helmet and camouflage gear.

Meanwhile, Yulia Tymoshenko, a former prime minister and one of the country’s most divisive figures, announced Thursday that she would run for president.

Tymoshenko, who was released from prison last month after the overthrow of her rival Yanukovych, is variously admired as an icon of democracy or detested as a self-promoting manipulator with a shady past.

This will be the 53-year old Tymoshenko’s second attempt to win the presidency. She narrowly lost to Yanukovych in 2010 and spent two years in jail on charges that many in the West considered politically motivated.

“I will be the candidate of Ukrainian unity,” Tymoshenko said in announcing she would join the May 25 election. “The west and center of Ukraine has always voted for me, but I was born in the east.”

While western regions of Ukraine favor closer ties to Europe, the eastern part of the politically divided nation has long aligned with neighboring Russia.

Tymoshenko, who is known for her trademark blond braid, generated new controversy this week after she was heard in a recorded telephone conversation using expletives and a derogatory term for Russians, and saying that Russia should be destroyed for its invasion and annexation of Crimea.

“I am hoping that I will use all of my connections and will get the whole world to rise up so that not even scorched earth would be left of Russia,” Tymoshenko said in the call, which was posted on YouTube.

Tymoshenko, writing on Twitter, suggested that some of the conversation was altered but appeared to confirm the general contents, and apologized for using expletives.

Since Yanukovych’s ouster, which the Kremlin has denounced as a coup supported by the West, the Fatherland Party has had a strong grip on the new provisional government.

Both the acting president, Oleksandr Turchynov, and Yatsenyuk are leading members of Fatherland. The party voted at a conference last year to nominate Tymoshenko as its candidate for president should she be able to run. At that point, elections were scheduled for early 2015. The parliament has since moved the elections to May.

Information for this article was contributed by Peter Leonard, Yuras Karmanau, Nataliya Vasilyeva , Juergen Baetz, Deb Reichmann, Donna Cassata, Cara Anna and Edith M. Lederer of The Associated Press; by Kathleen Hunter, Daryna Krasnolutska, Daria Marchak, Roxana Tiron, Sandrine Rastello, Julianna Goldman, Volodymyr Verbyany and Andra Timu of Bloomberg News; and by Patrick Reevell and David M. Herszenhorn of The New York Times.

Front Section, Pages 1 on 03/28/2014