The Kremlin on Monday praised Rex Tillerson, front-runner to be U.S. President-elect Donald Trump's pick for Secretary of State, as highly professional.

Trump is expected to name Tillerson, chief executive of Exxon Mobil, as Washington's top diplomat, a source familiar with the situation said on Saturday. The appointment would add another figure in Trump's cabinet with close ties to Russia.

"As part of his duties as head of one of the biggest oil companies, he had contacts with our representatives," Kremlin spokesman Dmitry Peskov, said on a conference call with reporters. "He carries out his duties in a highly professional way." Asked about how close Tillerson is to Putin, Peskov said: "They had working meetings. Indeed, the president received Tillerson several times. As for assertions about whether he will treat the Russian Federation well or badly, there is a big difference between being secretary of state and being head of a company, albeit a large one," said Peskov.

As Exxon Mobil CEO, Tillerson has worked on energy projects in Russia and has built close ties with Igor Sechin, the chief executive of Russian oil major Rosneft who is also a close Putin associate.

Despite Kremlin's satisfaction, when the news of Tillerson's candidate emerged, it raised a lot of reaction and suspicion among the U.S. politicians. Robert Menendez, one of the senior Democrats in the foreign relations committee said, "With Rex Tillerson as our secretary of state, the Trump administration would be guaranteeing Russia has a willing accomplice in the president's cabinet guiding our nation's foreign policy," referring to Tillerson's order of friendship awarded by Russian President Vladimir Putin.