At a White House news conference on Thursday, he vowed to bypass the media and take his message "straight to the people".
Nearly a month into his presidency, Mr Trump said his new administration had made "significant progress" and took credit for an optimistic business climate and a rising stock market.
He pushed back against widespread 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 travellers from seven predominantly Muslim nations.
"This administration is running like a fine-tuned machine," Mr Trump declared. The president said that he would announce a "new and very comprehensive order to protect our people".
Meanwhile, the president announced that Alexander Acosta, dean of the Florida International University law school, would be his nominee for Labour secretary.
That came a day after fast-food executive Andrew Puzder withdrew after losing support among Republican senators.
If confirmed, Mr Acosta would be the first Hispanic member of Mr Trump's Cabinet.
Mr Trump, a reality television star and real estate mogul who was elected as an outsider intent on change, opened a hastily arranged news conference to attack 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," Mr Trump said.
As for his inner circle, Mr Trump is also expected to soon name a new national security adviser following this week's ousting of Michael Flynn, who the White House said had misled Vice President Mike Pence about Mr Flynn's contacts with Russia.
Mr Trump is said to favour Vice Admiral Robert Harward, a former Navy SEAL, according to a White House official.
Mr Harward met with top White House officials last week and has the backing of Defence Secretary Jim Mattis.
Earlier in the day, Mr Trump had a breakfast meeting with some of his staunchest House supporters.
The White House has said Mr Trump asked for Mr 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 US before Mr Trump's January 20 inauguration. Mr Flynn previously had denied those conversations to Mr 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, Mr 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".
Throughout the news conference in the East Room of the White House, the new president delivered repeated criticism of the news media.
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.
Mr Trump called Paul Manafort, his former campaign manager who has ties to Ukraine and Russia, a "respected man".
Mr Trump called the reports a "ruse" and said he had "nothing to do with Russia". Mr Trump added: "Russia is fake news. This is fake news put out by the media."
Amid reports of widespread leaks within his administration, Mr 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.
He said: "Those are criminal leaks," adding: "The leaks are real. The news is fake."
The president said his ousted national security adviser, Mr Flynn, was "just doing his job", but said he was "not happy" with how information about Mr Flynn's phone call to a Russian diplomat was relayed to Mr Pence.
But Mr Trump said what Mr Flynn did "wasn't wrong" and said he had identified a strong replacement for Mr Flynn, which made the decision to let him go easier.