In his confirmation hearing before the U.S. Senate, retired Marine General James Mattis said he had stark concerns about Russia, directly labeling that country an adversary of America, and accusing Russian leader Vladimir Putin of having one main goal with regards to the United States.

"The most important thing is that we recognize the reality of what we deal with, with Mr. Putin, and we recognize that he is trying to break the North Atlantic alliance," Mattis said.

"If we did not have NATO today, we would need to create it," Mattis told Sen. Bill Nelson (D-FL).

With lawmakers in both parties raising red flags in recent weeks about how a Trump Administration might change U.S. policy with regards to Russia, Mattis faced repeated questions about Mr. Trump's commitment to NATO allies who feel threatened by Moscow.

"He understands where I stand," Mattis said, as he made clear he sees Russia, China and Islamic terrorism as the three major security threats to the United States, and the world.

On Russia, Mattis said it would be wrong to ignore the history of American outreach efforts to Moscow.

"Since Yalta, we have a long list of times that we have tried to engage positively with Russia," Mattis said.

"We have a relatively short list of successes in that regard," he added.

That assessment was echoed by Sen. John McCain (R-AZ), who has been highly critical of friendly statements by the President-Elect about Putin and Russia.

"I've watched three Presidents commit themselves to new relationships with Vladimir Putin; all three have been an abysmal failure," McCain said to Mattis.

Russia was also a top issue in a separate hearing before the Senate Intelligence Committee, where Rep. Mike Pompeo (R-KS) - President-Elect Trump's pick for CIA Director - was quizzed about Russian interference in the 2016 elections.

Pompeo said he had been briefed on the recent report into Russian hacking actions, and said he fully accepted the conclusions, which have drawn fire from some Trump supporters.

"Everything I have seen suggests to me that the report has an analytical product that is sound," Pompeo said of the intelligence investigation into Russia's cyber meddling.

The Kansas Republican was also asked his views on Wikileaks - he said he found the internet group that strongly backed Donald Trump is not a "credible source of information."

Pompeo's hearing got off to a somewhat odd start, as the lights in the room, and the television feed suddenly went off - just as the top Democrat on the panel mentioned Russia's election interference.