Several key U.S. lawmakers endorsed the next major step in American assistance to Ukraine on Tuesday, encouraging the White House to move forward with a plan to send M1 Abrams tanks to combat Russian aggression.

'Seldom in the history of modern warfare has so much depended on so few tanks,' Republican Lindsey Graham told reporters Tuesday after returning from a congressional trip to Ukraine. 'Three hundred tanks given to the Ukrainians who have an ability to take any weapon system and maximize its benefit.'

Despite the difficulties of running M1 Abrams tanks on jet fuel, the Biden administration is reportedly weighing sending the tanks to Ukraine, hoping it would increase chances of Germany sending its own Leopard tanks.

Poland announced Monday it would seek German approval to send tanks from its stock of Leopards, and Great Britain announced last week it would send Challenger 2 tanks. Ukrainian officials said Challenger 2 tanks were 'not sufficient to meet operational goals.'

FILE - An M1 Abrams crosses a bridge in Hell, Norway, Oct. 21, 2018, during a military exercise. (U.S. Navy photo)

Ukraine has consistently asked Western nations to supply tanks to defend itself against Russia. Last week at a meeting of NATO officials, Germany said it would consider supplying Leopard 2s - seen as the most advanced tanks - if the United States would supply M1 Abrams.

German news outlet Der Spiegel and others cited unconfirmed reports late Tuesday that the German government has decided to send the Leopard 2 tanks. American news service The Associated Press reported officials saying the U.S. will announce it will send M1 Abrams tanks as soon as this Wednesday.

'If press reports are true, I am very pleased with the Biden Administration's apparent decision to send Abrams tanks to help Ukraine evict Russia from Ukrainian soil,' Graham said in a statement.

'The Ukrainians can win if they have the tools that are necessary - beginning with tanks,' said Democratic Senator Richard Blumenthal, who was also part of the delegation that met with President Volodymyr Zelenskyy in Ukraine. 'The Leopard 2 tanks are important because they are there. They're in Europe, thousands of them within easy transport, training, fueling. They are essential. And just very bluntly, if it takes sending three, five, 10 Abrams tanks there, let's do it.'

The Pentagon said earlier Tuesday that M1 Abrams are 'complex weapons systems that are challenging to maintain.' Brigadier General Patrick Ryder told reporters, 'Our focus has been on providing Ukraine with capabilities it can employ right now on the battlefield.'

Senate Minority Leader Mitch McConnell warned on the Senate floor Tuesday that the West's failure to act could have devastating consequences.

FILE - People hold signs referencing Leopard tanks being sent to Ukraine, at a demonstration in Berlin, Germany, Jan. 20, 2023.

'Germany has not only resisted calls to send Leopard 2 tanks to Ukraine but has also prevented other European nations to transfer their own German-produced Leopards to Ukraine. Time is short, and while Berlin agonizes over its own decision whether to provide Leopards to Ukraine, it should proactively and explicitly make clear that other allies are free to do so,' McConnell said.

He added that the Biden administration's 'latest deliveries failed to include the longer-range missiles and more sophisticated munitions that Ukraine has been requesting for months. Mr. President, Ukraine's brave resistance deserves our continued praise. But more importantly, it needs our concrete and consistent material support.'

Ukraine on Tuesday marked the 11-month anniversary of the Russian invasion. Since then, the United States has provided nearly $50 billion in humanitarian, economic and military aid. But U.S. assistance to Ukraine could face a roadblock in the House of Representatives, where Republicans holding the majority have expressed concern about oversight of the aid. Speaker of the House Kevin McCarthy said last year the United States would not continue to write a 'blank check' on aid while Americans face a difficult domestic economic situation.

But Graham pushed back against the perception the aid is not being properly managed.

'We're very reassured that that our military assistance is going to where it should be going to and that accountability and transparency is there,' Graham said. 'To my House colleagues, to those who believe we shouldn't write a blank check, I agree. To those who have concerns about what's going on in Ukraine - go. Don't talk about it in Washington, get on a plane, get on a train, rest up, drink a lot of water, take your vitamins, and they will open up the books.'