NEW YORK (CBSNewYork/AP) — The top Senate Republican said Monday that Congress will investigate a CIA assessment that Russia interfered in the November election on behalf of Donald Trump, an intelligence conclusion that the incoming commander in chief has called “ridiculous.”

Majority Leader Mitch McConnell (R-Kentucky) told reporters that an inquiry would be conducted by the Senate intelligence panel. Two key Senate Republicans, John McCain of Arizona and Lindsey Graham of South Carolina, a leading Trump critic, have joined with two Democrats in seeking a bipartisan investigation into the Kremlin’s activities during the election.

“Obviously any foreign breach of our cybersecurity measures is disturbing, and I strongly condemn any such efforts,” McConnell said.

Unlike Trump, who has expressed admiration for Russian leader Vladimir Putin, McConnell said flatly, “The Russians are not our friends.”

The CIA recently concluded with “high confidence” that Russia sought to influence the U.S. election on behalf of Trump, raising red flags among lawmakers concerned about the sanctity of the U.S. voting system and potentially straining relations at the start of Trump’s administration.

McCain said Monday on “CBS This Morning” that probes are essential because hacking could be a new form of warfare.

“It’s all part of the larger issue of the cyber threat that we face from Russia, China and other countries,” McCain said. “It’s a threat to our national security.”

Also on “CBS This Morning,” incoming Senate Democratic leader Charles Schumer (D-N.Y.) said he doesn’t want the investigation to become political.

“This is serious stuff — when a foreign power tries to intervene to influence an election,” he said. “It’s gotten worse and a bipartisan investigation that’s not aimed at one specific instance but looks at the broad scope of this is just what’s needed.”

U.S. Sen. Cory Booker (D-N.J.) also called for an investigation, WCBS 880’s Peter Haskell reported.

“This is a legal action taken by a foreign government to undermine our democracy — one of the fundamental bedrocks of our democracy — the election process,” Booker said.

But as CBS2’s Dick Brennan reported, the Trump camp believes democrats are trying to replay the election.

“I think it’s ridiculous. I think it’s just another excuse,” Trump said on Fox News Sunday. “I don’t believe it.”

Trump went on to tweet Monday that “it’s very hard to determine who was doing the hacking.” He added that if his campaign had lost the election and “we tried to play the Russia/CIA card. It would be called conspiracy theory!”

“It’s always someone other than Hillary Clinton’s fault as to why she lost, and we’re not going to accept that,” said Trump spokeswoman Kellyanne Conway. “We are not going to allow people to insinuate or indeed insult the president-elect and the trememdous victory that he had ”

Trump has now picked a fight with U.S. intelligence.

“He believes that the CIA is a political institution and he’s going to have to learn that it’s not,” former CIA Deputy Director Mike Morrell told “CBS This Morning.”

Trump on Sunday also praised ExxonMobil chief executive officer Rex Tillerson, who has emerged as the leading contender to lead the State Department. During his campaign, Trump weathered turbulent relations with fellow Republicans but has since forged a more united front with GOP lawmakers since his November victory over Hillary Clinton.

Russia expects to figure prominently at the start of a week in which Trump is expected to name more members of his Cabinet, which also has vacancies in the departments of Energy, Agriculture and Veterans Affairs.

Trump’s transition team announced Monday that his choice to head the Department of Homeland Security is, as expected, Gen. John Kelly. Kelly is a former commander of U.S. Southern Command with “unique insight into some of the challenges the United States faces at its southern border,” the announcement said.

“It’s a matter of concern to me that he has such a close personal relationship with Vladimir Putin,” McCain said of Tillerson. “And obviously they’ve done enormous deals together.” In an interview with CBS’ “Face the Nation,” McCain said, “That would color his approach to Vladimir Putin and the Russian threat.”

Russia expects to figure prominently at the start of a week in which Trump is expected to name more members of his Cabinet, which also has vacancies in the departments of Energy, Agriculture and Veterans Affairs.

During his campaign, Trump weathered turbulent relations with fellow Republicans but has since forged a more united front with GOP lawmakers since his November victory over Hillary Clinton.

In his wide-ranging interview with Fox News Sunday,’ Trump dismissed those concerns as little more than partisan griping. “I think the Democrats are putting it out because they suffered one of the greatest defeats in the history of politics in this country. And frankly, I think they’re putting it out,” Trump said.

The incoming president said he did not necessarily oppose calls from President Barack Obama for an inquiry into the 2016 campaign hacking but said it should not be solely focused on a single culprit.

“If you’re going to to do that, I think you should not just say ‘Russia.’ You should say other countries also, and maybe other individuals,” he said. The White House has said the probe would focus on any breaches by other countries along with hacking committed in previous elections.

Trump’s decision-making on whom to select for secretary of state has stretched out over several weeks. He has been considering former Massachusetts Gov. Mitt Romney, a one-time vocal Trump critic, Sen. Bob Corker of Tennessee, who leads the Foreign Relations Committee, and Tillerson, the oil industry executive who met twice with Trump during the past week.

In the television interview, Trump pointed to Tillerson’s deep relations with Moscow as a selling point. As ExxonMobil’s head, he maintained close ties with Russia and was awarded by Putin with the Order of Friendship in 2013, an honor for a foreign citizen.

“A great advantage is he knows many of the players, and he knows them well. He does massive deals in Russia. He does massive deals for the company,” Trump said, while also citing Corker and Romney.

“These are all very different types of people,” he said. “But when you ask me about Rex, I mean, he’s a world-class player. There’s no question about it.” By Sunday afternoon, Tillerson had still not been formally offered the job, according to a person with knowledge of the process who spoke on condition of anonymity.

Democrats have warned that plucking Tillerson for State would put the leader of the world’s largest oil company in a pivotal role on issues like climate change and the future of the Keystone XL pipeline. They also question whether he would apply diplomatic pressure on Russia’s conflict with Ukraine.

Sen. Bob Casey, D-Pa., said the developments “raise serious questions about whether the incoming administration will adequately stand up to Russia’s aggression.”

But Conway said, “We look at this as an asset, not a liability.”

“In that it’s not like he’s hanging around with Vladimir Putin on the weekends at dinner parties,” she said. “It’s that he understands Russia; he’s already doing business there.”

The prospect of Tillerson also received a cool reception from some Republican members of the Senate Foreign Relations Committee, which would consider his nomination.

Sen. Marco Rubio of Florida, who unsuccessfully challenged Trump for the GOP nomination, wrote on Twitter, “Being a ‘friend of Vladimir’ is not an attribute I am hoping for from a #SecretaryOfState.”

Meanwhile Monday, a former rival met with Trump at Trump Tower and is supporting his picks.

“People recognize the opportunity that our new president-elect has to really make a huge impact on people’s lives in this country and on events around the world,” said former Hewlett-Packard chief executive officer Carly Fiorina, who ran in the GOP primary.

Trump said he will announce his pick for secretary of state on Tuesday.

(TM and © Copyright 2016 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2016 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)