The former oil executive set to be the United States' top diplomat, Rex Tillerson, said Wednesday the world faces "considerable threats" from a number of adversaries, including Russia.
Questions about Russia and Tillerson's relations with the country took center-stage during Tillerson's confirmation hearing amid allegations that Russia meddled in the US presidential election.
Former ExxonMobil boss Tillerson, nominated last month by US president-elect Donald Trump for the position of secretary of state, told the Senate Foreign Relations Committee that Russia is "clearly an unfriendly adversary."
But when asked whether he would label Russian President Vladimir Putin a war criminal, he said, "I would not use that term."
Senator Marco Rubio, a Republican who ran against Trump for his party's nomination for president, said he found it "discouraging" that he couldn't say that about Putin, which Rubio said "is globally accepted."
Tillerson preferred to cite the need for engagement to redefining the US relationship with Moscow.
He acknowledged however that in recent years Russia had given NATO allies good reason for alarm by invading Ukraine and supporting Syria's brutal regime.
"Russia must be held to account for its actions," he said.
Rubio told repoters outside the hearing that he is not certain he will support Tillerson, citing human rights considerations.
On Russia's annexation of Crimea, Tillerson said that "was a taking of territory that was not theirs." He said he would have recommended that Ukraine put all its military assets on its eastern border and that the US provide defensive weapons to them.
"I think what Russian leadership would have ... understood is a powerful response that indicated, yes, you took the Crimea, but this stops right here." Tillerson said.
Trump garnered controversy when he nominated the Texas-born oilman, with critics pointing to Tillerson's lack of political experience and close ties to Russia.
Tillerson, who represented ExxonMobil's interests in Russia in the 1990s, told senators Wednesday that dialogue and engagement between Moscow and Washington are critical to redefining the relationship.
"Russia today poses a danger, but it is not unpredictable in advancing its own interests," Tillerson said.
He also called the finding announced last week by several top US intelligence officials that Russia had meddled in the US presidential election "troubling."
Tillerson spent much of the hearing answering questions about ExxonMobil and its activities in Russia, which awarded Tillerson the Order of Friendship in 2013, including whether the company had sought a relaxation of sanctions the US has levelled on it.
He said he had never lobbied against sanctions personally and he continued to believe they are a good tool, but "having poor and ineffective sanctions can have a worse effect than having no sanctions at all if they convey a weak response."
Speaking more broadly about international affairs, Tillerson repeatedly said he believes what's been absent in recent decades is American leadership, and both the American people and US allies look forward to its return.
"To achieve the stability that is foundational to peace and security in the 21st century, American leadership must not only be renewed, it must be asserted," Tillerson said.
Tillerson also mentioned strained relations with China, Iran and North Korea and said radical Islam poses a grave risk to the stability of nations.
When questioned about his loyalty to ExxonMobil, he pledged to separate his business background from his new role if confirmed.
The Senate has the power to reject Tillerson, but this is considered unlikely given that the Republican Party's majority.