WASHINGTON – President Donald Trump mounted a vigorous defense of his presidency Thursday, pushing back against media reports that his campaign advisers had inappropriate contact with Russian officials and vowing to crack down on the leaking of classified information.

Nearly a month into his presidency, Trump said in a free-wheeling White House news conference that his new administration had made “significant progress” and took credit for an optimistic business climate and a soaring stock market.

The president denounced media reports of a chaotic start to his administration marked by a contentious executive order — now tied up in a legal fight — to place a ban on travelers from seven predominantly Muslim nations.

“This administration is running like a fine-tuned machine,” Trump declared. He said he would announce a “new and very comprehensive order to protect our people.”

Throughout the news conference in the East Room of the White House, the new president delivered repeated criticism of the news media, accusing it of being “out of control” and promising to take his message “straight to the people.”

He dismissed recent reports in The New York Times and CNN that Trump campaign aides had been in contact with Russian officials before his election. Trump called Paul Manafort, his former campaign manager who has ties to Ukraine and Russia, a “respected man.”

Trump called the reports a “ruse” and said he had “nothing to do with Russia.” Trump added, “Russia is fake news. This is fake news put out by the media.”

Amid reports of widespread leaks within his administration, Trump also warned that he would clamp down on the dissemination of sensitive information, saying he had asked the Justice Department to look into the leaks. “Those are criminal leaks,” adding, “The leaks are real. The news is fake.”

Mr. Trump also says it makes sense for the U.S. to get along better with Russia because both are nuclear powers.

The president said during a lengthy White House news conference that the risks of conflict with the country are enormous.

Trump says, “We’re a very powerful nuclear country, and so are they.”

He says he’s been briefed on the issue and adds, “Nuclear holocaust would be like no other.”

Trump also says he won’t forecast how he’ll respond to provocations from Russia, North Korea or Iran. He says that’s to maintain the element of surprise.

Additionally, Mr. Trump is defending the rocky rollout of his travel ban, which judges have put on hold while they weigh its legality.

He calls the rollout “very smooth” and “perfect” but says it ran into “a bad court.”

Trump says he wanted to do the same order but have it take effect after a month or so, but he says he was advised by Homeland Security Secretary John Kelly not to do that because it would give people with bad intent time to flow into the country.

He says, “That’s why we did it quickly.” Waiting, he says, “would have wasted a lot of time, and maybe a lot of lives.”

The president announced that Alexander Acosta, the dean of the Florida International University law school, would be his nominee for Labor secretary. It came a day after fast-food executive Andrew Puzder withdrew his nomination for Labor after losing support among Republican senators.

Trump, a reality television star and real estate mogul who was elected as an outsider intent on change, opened the hastily arranged news conference to bash coverage by the news media. He accused reporters of not telling the truth and only serving special interests.

“The press has become so dishonest that if we don’t talk about it, we are doing a tremendous disservice to the American people,” Trump said.

The president said his ousted national security adviser, Michael Flynn, was “just doing his job,” but said he was “not happy” with how information about Flynn’s phone call to a Russian diplomat was relayed to Vice President Mike Pence.

But Trump said what Flynn did “wasn’t wrong” and said he had identified a strong replacement for Flynn, which made the decision to let him go easier.

Trump is said to favor Vice Admiral Robert Harward, a former Navy SEAL, as his next national security adviser, according to a White House official. Harward met with top White House officials last week and has the backing of Defense Secretary Jim Mattis. He is slated to meet with officials later Thursday.

Earlier in the day, Trump had a breakfast meeting with some of his staunchest House supporters.

The White House has said Trump asked for Flynn’s resignation because he had misled Vice President Mike Pence over his dealings with Russia and whether he had discussed sanctions with Russia’s ambassador to the U.S. before Trump’s Jan. 20 inauguration. Flynn previously had denied those conversations to Pence and other top officials.

On Thursday, he warned in a pair of tweets that “low-life leakers” of classified information will be caught. As journalists were being escorted out of the breakfast meeting, Trump responded to a reporter’s question on the subject by saying: “We’re going to find the leakers” and “they’re going to pay a big price.”