WASHINGTON: US senators on Sunday (Jul 13) touted a bipartisan Bill that would arm President Donald Trump with "sledgehammer" sanctions to use against Russia, ahead of a visit by the US special envoy to Ukraine.

Trump has indicated he would be open to the sanctions Bill as relations with Russian counterpart Vladimir Putin grow increasingly frosty.

US special envoy Keith Kellogg is due to begin his latest visit to Ukraine while Trump said he would make a "major statement ... on Russia" on Monday.

Republican Senator Lindsey Graham said he had majority backing in the Senate for his Bill, which was gaining momentum as Washington-led peace efforts in Ukraine have struggled to make headway.

The Bill would allow Trump "to go after Putin's economy, and all those countries who prop up the Putin war machine", Graham told broadcaster CBS News.

Trump, who has repeatedly said he is "disappointed" with Putin as Moscow unleashed deadly barrages of missiles against Kyiv, has hinted he might finally be ready to toughen sanctions.

Trump held off for the past six months while he tried to persuade Putin to end the war.

But the Republican president's patience appears to be wearing thin, telling reporters during a Cabinet meeting at the White House Tuesday that Putin was talking "a lot of bullshit" on Ukraine.

Last week, Trump also agreed to send Zelenskyy more weapons, including through a deal with NATO, which would involve the alliance purchasing US weapons to send to Ukraine.

On Thursday, Trump appeared to back the Bill without detailing whether he would use it to slap sanctions on Moscow.

"They're going to pass a very major and very biting sanctions Bill, but it's up to the president as to whether or not he wants to exercise it," Trump told broadcaster NBC.

Asked during a Cabinet meeting about his interest in the Bill, Trump said: "I'm looking at it very strongly."

"This congressional package that we're looking at would give President Trump the ability to impose 500 per cent tariffs on any country that helps Russia," said Graham, adding that those could include economies that purchase Russian goods like China, India or Brazil.

"This is truly a sledgehammer available to President Trump to end this war," said Graham.

"Without a doubt, this is exactly the kind of leverage that can bring peace closer and make sure diplomacy is not empty," the Ukrainian leader said about the proposed bill in an X post.

Graham and Democratic Senator Richard Blumenthal were to meet NATO secretary-general Mark Rutte on Monday night.

Blumenthal told CBS News they would also discuss the legally thorny issue of unlocking frozen Russian assets in Europe and the United States for access by Ukraine.

"The US$5 billion that the United States has also could be accessed, and I think it's time to do it," said Blumenthal.