The former CEO of US oil giant Exxon Mobil said in his opening statement that he was “clear-eyed” on Russia.

“Russia today poses a danger, but it is not unpredictable in advancing its own interests. It has invaded Ukraine, including the taking of Crimea, and supported Syrian forces that brutally violate the laws of war. Our Nato allies are right to be alarmed at a resurgent Russia,” he said.

"We [the US and Russia] aren't likely to ever be friends ... Our value systems are starkly different,” he added.

In response to senators’ questions, he said that if he had been in office when Russia seized Crimea, then the US and Nato allies would have sent Ukraine defensive weapons to help it stop Russian forces.

"If Russia acts with force ... they require a proportional show of force to indicate to Russia that there will be no more taking of territory,” he said.

“What the Russian leadership would have understood is a powerful response,” he said, adding that his message to Russian leader Vladimir Putin would have been: “Yes, you took Crimea, but this stops right here.”

He said US president Barack Obama, who declined to arm the Ukrainian military, had been too dove-ish.

“It was in the absence of American leadership that this door [to Russian aggression in Ukraine] was left open,” Tillerson said.

The 64-year old, in his Exxon Mobil days, had close ties to Moscow and was awarded an Order of Friendship medal by the Kremlin in 2013.

The oil firm has been accused of lobbying against US sanctions on Russia over Ukraine, an allegation it denied in a statement on Wednesday.

Tillerson’s comments also come amid concerns that US president-elect Trump, who is an outspoken fan of Putin, will undo the US sanctions, leaving the EU alone in its bid to use economic measures to curtail Russia’s behaviour.

Status quo

Tillerson declined to say explicitly if the US would uphold its punitive measures.

"I would leave things in the status quo so we are able to convey this can go either way,” he said.

He said sanctions were “a powerful tool and … an important tool in terms of deterring additional action”.

He said he looked forward to working with the Senate “particularly on the construct of new sanctions” against Russia, if need be.

He also said that “we need to move Russia from being an adversary always to being a partner sometimes”, however, and that sanctions “harm American businesses”.

Asked if he would endorse additional sanctions on Russians deemed responsible for cyber-attacks on the US elections, he was equally evasive.

“Certainly this most recent manifestation, and I think the new threat posed in terms of how Russia has used this as a tool, that introduces even another element of threat, but cyber-attacks are occurring from many nations,” he said.

He declined to say if he believed in the recent intelligence leaks that said Russia had material which it could use to blackmail Trump.

He also declined to name Putin as a “war criminal” over Russian bombing of civilians in Syria, saying he did not yet have the security clearance to get the necessary intelligence briefings.

Trump himself in a press conference the same day dismissed the blackmail leak as “fake … sick … phoney”.

He admitted that Russian hackers had targeted the US election, however. He also promised to take a tough line on Putin if the need arose.

“Do you honestly believe that Hillary would be tougher on Putin than me?” he said, referring to Hillary Clinton, who had run against him for the White House.

“Russia will have much greater respect for our country when I am leading it than when other people have led it. You will see that," he said.

China confrontation?

Tillerson, in his hearing, also indicated that he was willing to confront China on its military expansion in the South China seas.

He said its construction of military bases on man-made islands was “akin to Russia’s taking of Crimea”.

“We’re going to have to send China a clear signal that, first, the island-building stops and, second, your access to those islands also is not going to be allowed,” he said.

On climate change, Exxon Mobil has lobbied against the scientific consensus that human activity causes global warming.

Trump has also said he did not believe the scientific findings, but Tillerson indicated that the US should not walk away from the Paris accord on limiting temperature rises.

Climate change real

"The risk of climate change does exist and the consequences of it could be serious enough that action should be taken," he said.

He said Israel remained America’s most important ally in the Middle East and criticised a recent UN resolution urging it to halt settlement expansion.

He also said that he would push for a “full review” of the EU-brokered Iran nuclear non-proliferation deal.