The U.S. Senate confirmed Rex Tillerson as President Donald Trump's secretary of state on Feb. 1, filling a key spot on the Republican president's national security team despite concerns about the former ExxonMobil Corp. (NYSE: XOM) CEO's ties to Russia.

In the vote, 56 senators backed Tillerson, and 43 voted no. The tally was largely along party lines, with every Republican favoring Tillerson, along with four members of the Democratic caucus, Sens. Heidi Heitkamp, D-N.D., Joe Manchin, D-W.V., and Mark Warner, D-Va., as well as Angus King, I-Maine.

Sen. Chris Coons, D-Del., did not vote.

Senate Democrats had tried, but failed, to delay the vote because of Trump's executive order banning immigration from seven majority-Muslim countries and temporarily halting the entry of refugees.

They said they wanted to ask Tillerson more questions about the issue after Trump signed the order on Jan. 27.

Senators had also expressed concerns over Tillerson's ties to Russia after he spent years there working for the oil company. Some faulted Tillerson for failing to promise to recuse himself from matters related to ExxonMobil businesses for his entire term as secretary of state, rather than only the one year as required by law.

Republicans said they thought Tillerson would be a strong leaders as the country's top diplomat. They also said it was important to fill key slots on Trump's national security team quickly.