US President Donald Trump has said he accepts US intelligence agencies' conclusion that Russia interfered in the 2016 election - despite declining to do so just a day ago.
He said he had misspoken on Monday and had meant to say he saw no reason why it was not Russia that meddled.
The original comments, after he met Russian President Vladimir Putin in Helsinki, drew a barrage of criticism.
Even some of Mr Trump's allies had urged him to clarify his stance.
In his latest remarks, he added that he had "full faith and support" in US intelligence agencies.
Secretary of State Mike Pompeo is to appear before Congress next week to answer questions on what happened during Mr Trump's two-hour meeting with President Putin on Monday.
Analysis by the BBC's Anthony Zurcher in Washington
Does Donald Trump believe in ominous metaphors? As he affirmed his support for US intelligence agencies, the lights went to black in the White House conference room.
Once order was restored, he said he had been in the dark as to why a storm had swirled around his presidency since his Helsinki summit with Vladimir Putin. It was, he said, because he had misspoken.
That is going to be hard for many of the president's critics to swallow, however. Even if he did mean to say, "I don't see a reason why it wouldn't be Russia", it is a pretty weak way to confront the head of a nation accused of targeting the heart of American democracy.
What is more, the context of the president's comments make a simple slip of the tongue seem less likely.
At the very least, the president gave his supporters some material to rally around.
The damage, however, has been done. Mr Trump can give as many White House statements as he likes, but on the biggest stage - standing beside the Russian president - he fumbled. All the explanations cannot change that.
What Trump said then...
The controversy centres on a response he gave to a question at a news conference on Monday following the summit with Mr Putin.
This is an extract from the transcript posted by the White House.
REPORTER: President Putin denied having anything to do with the election interference in 2016. Every US intelligence agency has concluded that Russia did. My first question for you, sir, is, who do you believe?
TRUMP: My people came to me... they said they think it's Russia. I have President Putin; he just said it's not Russia. I will say this: I don't see any reason why it would be.
.... what he says now
Mr Trump said he had reviewed the transcript and realised he needed to clarify.
"In a key sentence in my remarks, I said the word 'would' instead of 'wouldn't," he said.
"The sentence should have been: 'I don't see any reason why I wouldn't' or 'why it wouldn't be Russia'. Sort of a double negative."
The US president added: "I accept our intelligence community's conclusion that Russia's meddling in the 2016 election took place. Could be other people also. A lot of people out there."
Mr Trump said that the interference had had no impact on the election, in which he defeated Hillary Clinton.
However, he did not respond when reporters asked him if he would condemn Mr Putin.
During the press conference with President Putin - in the same answer as the transcript above - Mr Trump went on to say: "President Putin was extremely strong and powerful in his denial today. And what he did is an incredible offer; he offered to have the people working on the case come and work with their investigators with respect to the 12 people. I think that's an incredible offer."
On Wednesday, Mr Trump said in a tweet that Russia had "agreed to help with North Korea", adding that "the process is moving along".
"There is no rush, the sanctions remain! Big benefits and exciting future for North Korea at end of process!" the president wrote.
He said that his meeting with Mr Putin was "positive" and "may prove to be, in the long run... a success". He added that because he "got along" with the Russian leader, it "bothered many haters".
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How great is the outrage?
Chuck Schumer, leader of the opposition Democrats in the Senate, said Mr Trump's retraction of his previous comments was a sign of weakness.
"He made a horrible statement, tried to back off, but couldn't even bring himself to back off," he told the Senate. "It shows the weakness of President Trump that he is afraid to confront Mr Putin directly."
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Republicans and Democrats alike were dumbfounded that Mr Trump had sided with Russia over his own intelligence officials after Monday's summit.
The US and Russia have been long-term adversaries and remain far apart on major issues. Some lawmakers were also upset that Mr Trump had refused to offer specific criticisms of Russia and Mr Putin, instead saying both countries were responsible for poor relations.
Even one of his most loyal Republican supporters, Newt Gingrich, said the comments were the "most serious mistake of his presidency".
House Republican Mike Turner accused Mr Trump of having damaged American foreign policy by failing to take Russia to task.
"He's given them a pass and is certainly not holding them accountable for what they're doing," he added.