A defiant President-elect Donald Trump on Wednesday adamantly denied reports that Russia had compromising personal and financial information about him, calling it a “tremendous blot” on the record of the intelligence community if material with any such allegations had been released.

The incoming president, in his first news conference since late July, firmly chided news organizations for publishing the material late Tuesday night.

After weeks of scoffing at reports that Russians had interfered in the election, he conceded publicly for the first time that Russia was likely responsible for the hacking of the Democratic National Committee.

“As far as hacking, I think it was Russia,” he said and quickly added that the United States is hacked by other countries as well, including China.

Mr. Trump’s extraordinary defense against the unsubstantiated intelligence report, just nine days before his inauguration, dominated a highly anticipated press conference in which he also announced a new cabinet member, detailed his plans to disentangle himself from his sprawling global business empire, gave his outlook on the future of the Obamacare health care law and said he would soon nominate someone to fill the vacancy on the U.S. Supreme Court.

“I think it’s a disgrace that information would be let out. I saw the information, I read the information outside of that meeting,” he said, a reference to a classified briefing he received last week from intelligence leaders. “It’s all fake news, it’s phony stuff, it didn’t happen,” Mr. Trump said in a news conference that saw him repeatedly joust with reporters. “It was gotten by opponents of ours.”

Asked about his relationship with Russian President Vladimir Putin, Mr. Trump boasted that it is an improvement over what he called America’s current “horrible relationship with Russia” and did not criticize the Russian leader for any interference in the election.

“If Putin likes Donald Trump, guess what, folks, that’s called an asset not a liability. I don’t know if I’m going to get along with Vladimir Putin — I hope I do — but there’s a good chance I won’t.”

Mr. Trump, Vice President-elect Mike Pence and incoming White House press secretary Sean Spicer also denounced the report about Russia’s influence on Trump. The incoming president said it never should have been released. He thanked some news organizations for showing restraint.

A U.S. official told The Associated Press on Tuesday night that intelligence officials had informed Mr. Trump last week about an unsubstantiated report that Russia had compromising personal and financial information about him. The official spoke on the condition of anonymity because the official was not allowed to publicly discuss the matter.

Mr. Trump and President Obama were briefed on the intelligence community’s findings last week, the official said.

Media outlets reported on the document late Tuesday and Mr. Trump denounced it on Twitter before his news conference as “fake news,” suggesting he was being persecuted for defeating other GOP presidential hopefuls and Democrat Hillary Clinton in the election.

The dossier contains unproven information about close coordination between Mr. Trump’s inner circle and Russians hacking into Democratic accounts, as well as unproven claims about unusual sexual activities by Mr. Trump among other suggestions attributed to anonymous sources, that could possibly make him a target of blackmail.

The Associated Press has not authenticated any of the claims.

Only days from his inauguration as the nation’s 45th president, Mr. Trump announced that he would nominate David Shulkin to lead the U.S. Department of Veterans Affairs, elevating him from his current role as a Veterans Affairs undersecretary.

He promised that a replacement for the health care overhaul would be offered “essentially simultaneously” with the repeal of President Obama’s signature health law — something that would be virtually impossible to quickly pass given the complexity of the policy changes.

Republicans agree on repealing the law, but nearly seven years after its passage have failed to reach agreement on its replacement.

Mr. Trump has repeatedly said that repealing and replacing “Obamacare” was a top priority, but has never fully explained how he plans to do it. House Speaker Paul Ryan has said that the House would seek to take both steps “concurrently.”

Turning to his plans to build a border wall along the southern border, Mr. Trump said he would immediately begin negotiations with Mexico on funding his promised wall after he takes office. He again vowed that “Mexico will pay for the wall,” but the United States would be reimbursed for putting up the money. Mr. Trump recommitted to his plans to impose a border tax on manufacturers who shut plants and move production abroad. While the tax policy could retain jobs, it would also carry the risk of increasing prices for consumers.

Mr. Trump also said he would probably name his choice to fill the vacancy left by the 2016 death of U.S. Supreme Court justice Antonin Scalia in about two weeks after the inauguration.

And he announced his plans for the future of the Trump Organization, bringing to the podium attorney Sheri Dillon of Morgan Lewis, who worked with the Trump Organization on the arrangement.

Ms. Dillon said the Trump Organization would continue to pursue deals in the United States, although Mr. Trump will relinquish control of the company to his sons and an executive, put his business assets in a trust and take other steps to isolate himself from his business. She said Mr. Trump “should not be expected to destroy the company he built.”

The move appears to contradict a previous pledge by the president-elect. In a tweet last month, Mr. Trump vowed to do “no new deals” while in office.

The lawyer said Mr. Trump would donate all profits from foreign government payments to his hotels to the U.S. treasury.

And pushing back against some ethics experts, Ms. Dillon said the so-called emoluments clause of the U.S. Constitution does not apply to foreign payments to Mr. Trump’s company. While some ethics officials have said that foreign leaders who pay for rooms and services at his various hotels would run afoul of the constitutional ban on foreign gifts or payments to the president, Ms. Dillon referred to it as a “fair-value exchange.”