Secretary of State nominee Rex Tillerson has expressed views at odds with President-elect Donald Trump's positions on key foreign policy issues like nuclear proliferation, trade deals, climate change and relations with Mexico.
In a nine-hour Senate confirmation hearing, the former chief executive of oil company Exxon Mobil said he favoured maintaining US sanctions against Russia for now and that NATO allies were right to be alarmed by Moscow's growing aggression.
Russia dominated much of the hearing because of concerns by Democrats and Republicans over Moscow's interference in the US presidential election and its 2014 annexation of Crimea from Ukraine and involvement in the Syrian civil war.
Questions soon moved to the threat posed by Islamic State, China's behaviour in the South China Sea, human rights and Tillerson's ability to make a clean break from a career at Exxon Mobil to become America's top diplomat.
Tillerson said his differences with Trump on some major issues would not necessarily put him at loggerheads with the White House.
He said everyone in Trump's Cabinet would have the chance to discuss issues "and the president will decide." He described himself as open and transparent.
In a stark departure from Trump, Tillerson said it would not be acceptable for some US allies to acquire nuclear weapons. He also did not see the need for a Muslim registry, saying he did not support targeting any particular group.
Asked by Democratic Senator Edward Markey about Trump's comments in interviews he would not oppose US allies including Japan obtaining nuclear weapons, Tillerson replied: "I do not agree."
Tillerson said he did not oppose the Trans Pacific Partnership trade deal, which Trump has criticised, but acknowledged the negotiated deal may not serve all US interests.
Tillerson, however, left room for broad reversals or changes to Obama administration policies, in line with Trump's positions, including trade with Cuba and the Iran nuclear deal, which he said ought to undergo a full review.
The hearing before the Senate Foreign Relations Committee was interrupted sporadically by protesters. Tillerson, 64, is expected to be confirmed by the Republican-controlled Senate.
Tillerson refused to call Russian President Vladimir Putin a war criminal and kept the door open to a possible change in US sanctions policy against Russia, saying he had not seen classified information on Russian meddling.
"I would leave things in the status quo so we are able to convey this can go either way," Tillerson said, suggesting "open and frank" dialogue with Moscow to better understand its intentions.
He blamed Russia's aggression toward Ukraine since 2014 on an "absence of American leadership" and said the United States should have taken stronger actions to deter Russia.
"I'm advocating for responses that will deter and prevent further expansion of a bad actor's behaviour," he said.
Tillerson said it was a "fair assumption" Putin was aware of Russian efforts to interfere in the US election. He said he had not discussed Russia policy with Trump, which Democratic Senator Robert Menendez said was "pretty amazing."
In a tense exchange, Republican Senator Marco Rubio pushed Tillerson on whether he believed Putin was a war criminal, in reference to Russia's military actions in support of Syria's government.
"I would not use that term," Tillerson said, adding: "Those are very, very serious charges to make and I would want to have much more information before reaching a conclusion."
