Washington DC - The US may soon change course in its policy towards Russia, South Carolina Senator Lindsey Graham told CBS on Sunday, as momentum for a new sanctions package continued to grow in Congress.

"A turning point regarding Russia's invasion of Ukraine is coming," the Republican senator said in an interview on Face The Nation.

President Donald Trump has been trying to bring Russian President Vladimir Putin to the negotiating table for months, Graham pointed out.

"He's left the door open regarding Russia. That door is about to close," he warned.

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Graham pointed to support in the Senate for sanctions against Moscow, as well as other countries that buy Russian products and "prop up the Putin war machine."

He said a congressional package was being discussed that would allow Trump to impose whopping 500% tariffs on any country that helps Moscow, and explicitly called out China, India, and Brazil.

Graham described the move as a "sledgehammer" that Trump could use to end the war in Ukraine.

Trump, who has been growing increasingly frustrated with Putin, also promised to make a "major statement" on Russia on Monday, while US Special Envoy for Ukraine Keith Kellogg is travelling to Kyiv for a week-long visit.

NATO Secretary General Mark Rutte and German Defense Minister Boris Pistorius are also expected in Washington on Monday.