The US Senate Foreign Relations Committee split along party lines today to endorse Rex Tillerson as the country's next secretary of state, setting up a confirmation vote in the full Senate that is all but guaranteed to succeed.

Republicans unanimously backed Tillerson in the 11-to-10 vote, after key Republicans who had voiced criticism of Tillerson opted to support his nomination.

Chief among them was Senator Marco Rubio, a committee member who announced that he would support Tillerson despite concerns about how Tillerson would approach Russia and other countries Rubio counts as human rights violators, resolving the final major question surrounding Tillerson's bid to be confirmed as the nation's top diplomat.

"My concern was that Mr Tillerson would be an advocate for, and would pursue a foreign policy of dealmaking, at the expense of traditional alliances and at the expense of the defence of human rights and democracy," Rubio explained to the committee today.

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Several Democrats on the Foreign Relations Committee expressed similar concerns, and elected not to support Tillerson's nomination on those grounds. Democrats also complained that Tillerson had not answered many of their questions directly, and expressed alarm that the former ExxonMobil chief had advocated a military response to several conflicts, from the annexation of Crimea to the ongoing dispute with Beijing in the South China Sea.

"In my view the secretary of state should be leading with more diplomacy, and I found it disturbing that that seemed to be not his first reaction," said committee ranking member Ben Cardin.

But Tillerson's confirmation was effectively sealed yesterday, when senators John McCain and Lindsey Graham, both of whom had criticised him strongly, announced they would support his bid in the full Senate.

Rubio announced his decision just hours before the Foreign Relations Committee voted on Tillerson.