Washington-One day after Trump announced Rex Tillerson as his nominee for U.S. secretary of state, lawmakers from both major parties have raised questions about Tillerson’s relationship with Russia, and getting the Senate’s confirmation is not expected to be easy.

Tillerson is the chief executive of Exxon Mobil who has close ties to the Russian government.

He could face questions over his own professional contacts. At least four Senate Republicans have said they have doubts about Tillerson because of his relationship with Russian President Vladimir Putin, who awarded Tillerson with the nation’s highest honor, the Order of Friendship, in 2013.

Senate Armed Services Committee Chairman John McCain, R-Ariz., called Tillerson’s ties to Putin, “a matter of concern.”

“It’s very well known that he has a very close relationship with (Russian President) Vladimir Putin,” said McCain, the Republican Party’s 2008 nominee for president.

Republicans will have a majority of just 52-48 in the Senate, and only a few defections from their ranks would block Tillerson if every Democrat also opposed him.

However, several Republican establishment figures, including former Secretaries of State James Baker and Condoleezza Rice and former Defense Secretary Robert Gates vouched for Tillerson, 64, who has spent more than 40 years at the oil company.

Rice and Gates, who have worked for Exxon as consultants, both issued statements of support on Tuesday.

Their backing could be crucial for Tillerson receiving the approval he needs in the Senate, where Republicans will have a slim majority when Trump takes office on Jan 20.

“The fact that Condi Rice, James Baker and Bob Gates are recommending Tillerson carries considerable weight,” said Republican Senator Jeff Flake, a member of the Senate Foreign Relations Committee.

By choosing Tillerson, Trump adds another person to his Cabinet and circle of advisers who may favor a soft line toward Moscow, which is under U.S. sanctions for its 2014 annexation of Crimea and at the center of allegations that it launched cyber-attacks to disrupt the U.S. presidential election.