Former Exxon Mobile Executive Rex Tillerson appears before the Senate Committee on Foreign Relations for his confirmation hearing for the post of Secretary of State on Capitol Hill in Washington, DC Wednesday January 11, 2017.

The U.S. Senate advanced the nomination of former Exxon Mobil Chief Executive Rex Tillerson on Monday to be President Donald Trump's secretary of State, moving closer to filling a key seat on the Republican's national security team despite partisan rancor over Trump's immigration order.

The vote was 56 to 43 to move toward a final confirmation vote after up to 30 hours' debate, putting a final vote very early on Wednesday, if senators do not agree to change the time.

The vote broke largely along party lines. Every Republican favored advancing the nomination and all but four members of the Democratic caucus voted against it.

The Senate's Democratic leader, Chuck Schumer, and several other members of the party tried, but failed, to delay considering Tillerson because of Trump's executive order banning immigration from seven mostly Muslim countries and temporarily halting the entry of refugees.