U.S. Secretary of State Marco Rubio asserted on Tuesday that President Donald Trump had made no concessions to Russia, dismissing criticism of the administration's Ukraine policy during a Senate hearing.

"He hasn't gotten a single concession," Rubio said of Russian President Vladimir Putin.

Rubio was responding to Senator Jeanne Shaheen, the top Democrat on the Senate Foreign Relations Committee.

She hit back that Trump, since returning to the White House, has given Putin more incentive to gain territory as he plays for time.

Due to Chinese support for Russia and "because President Trump has given away our leverage, Putin doesn't feel pressured to agree to a ceasefire in Ukraine," she said.

Rubio said that Trump, who spoke again to Putin by telephone on Monday, does not want to impose fresh sanctions on Russia -- a step taken on Tuesday by the European Union.

"If, in fact, it is clear that the Russians are not interested in a peace deal and they just want to keep fighting a war, it may very well come to that point," Rubio said.

Trump "believes that right now, if you start threatening sanctions, the Russians will stop talking, and there's value in us being able to talk to them and drive them to get to the table," Rubio said.