WASHINGTON, Dec 12, 2023 (BSS/AFP) - Ukrainian President Volodymyr Zelensky goes to Congress and the White House on Tuesday to press for more US military aid in battling the Russian invasion, but the Republican Party shows little sign of listening to his increasingly desperate pleas.

For much of the nearly two years that Ukraine has resisted President Vladimir Putin's onslaught, the United States has led a Western coalition sending billions of dollars in weaponry and ammunition.

But Republicans are ever-more openly rejecting the need to fund Ukraine, saying that President Joe Biden needs to devote more attention to domestic security, particularly to stopping illegal migration over the US-Mexican border.

The Republicans are also questioning whether Ukraine should keep fighting at all.

Zelensky, who arrived fresh from a diplomatic push with world leaders at the inauguration of Argentine President Javier Milei over the weekend, will meet Biden at the White House. They will also hold a joint press conference.

Biden is a key supporter of Zelensky, framing the Ukrainian war effort as part of a global struggle between democracies and aggressive autocracies.

But on Capitol Hill, Zelensky will face his real test when he addresses Republican and Democratic senators, and meets the new Republican speaker of the House, Mike Johnson.

In a speech on Monday at the National Defense University in Washington, Zelensky said that politics should not "betray" Ukraine's soldiers and he echoed Biden in saying that the struggle had global implications.

"When the free world hesitates, that's when dictatorships celebrate and their most dangerous ambitions ripen," he said. "They see their dreams come true when they see delays."

"Putin must lose," he said.

Zelensky also met the heads of the International Monetary Fund and World Bank as he seeks to shore up his nation's beleaguered economy.

The IMF announced the release of a new $900 million tranche in an ongoing long-term loan.

- Republicans sour on Ukraine -

Republican senators last week blocked a White House request for $106 billion in emergency aid primarily for Ukraine and Israel.

Conservatives said they would refuse the package for these close foreign allies unless Democrats and the White House also agreed to far-ranging immigration reforms.

One key Republican senator, James Lankford, was quoted by US media on Monday saying "we're not going to be able" to get a deal by the end of this week.

But the Republican right-wing, led by former president and 2024 presidential candidate Donald Trump, has dramatically soured in a much broader sense against Ukraine's cause.

Influential Republicans increasingly question why the United States is supporting what they describe as Ukraine's impossible ambition to drive back all of Russia's invading forces.

"What's in America's best interest is to accept Ukraine is going to have to cede some territory to the Russians and we need to bring the war to a close," Senator JD Vance, a close Trump ally, said Sunday.

He dismissed as "preposterous" White House warnings that allowing Russia to win in Ukraine would put other eastern European countries, including NATO members, at risk.

There should be no "blank check" for Ukraine, Vance said.

"You need to articulate what the ambition is. What is $61 billion going to accomplish that $100 billion hasn't?"