President Donald Trump accused the House Intelligence Committee's top Democrat Monday of criminally leaking sensitive information.
Trump's tweet comes as Democrats push to release a memo expected to rebut a Republican document of alleged FBI surveillance abuses.
"Little Adam Schiff, who is desperate to run for higher office, is one of the biggest liars and leakers in Washington, right up there with Comey, Warner, Brennan and Clapper! Adam leaves closed committee hearings to illegally leak confidential information. Must be stopped!" Trump tweeted.
Schiff quickly responded on Twitter.
"Mr. President, I see you've had a busy morning of 'Executive Time.' Instead of tweeting false smears, the American people would appreciate it if you turned off the TV and helped solve the funding crisis, protected Dreamers or...really anything else," the California Democrat tweeted.
Trump did not provide evidence that Schiff has illegally leaked confidential information. The White House did not immediately respond to a request for comment Monday morning.
A source with direct knowledge of the matter said Democrats plan to offer a motion at a Monday business meeting to release their memo. If approved, the matter would be sent to Trump, who would have five days to object to its release.
The four-page GOP memo alleges that the FBI improperly used information paid for in part by Hillary Clinton's campaign to obtain a Foreign Intelligence Surveillance Act warrant for then-Trump campaign foreign policy adviser Carter Page. Trump has said the memo "totally vindicates" him in the Russia probe.
At last week's meeting, Republicans blocked a Democratic attempt to release their memo at the same time as the memo spearheaded by Chairman Devin Nunes of California, with Republicans saying they had just been presented with a copy of the Democrats' document.
Republicans have since said they'd vote to release the Democratic memo, drafted by Schiff, a sign that the committee is likely to approve its release.
Later Monday morning, Trump praised Nunes, who served on his transition team.
"Representative Devin Nunes, a man of tremendous courage and grit, may someday be recognized as a Great American Hero for what he has exposed and what he has had to endure!" the President tweeted.
Trump has railed against leaks during his first year in office. In November, Attorney General Jeff Sessions said the Justice Department was conducting more than two dozen investigations into classified leaks of information, a sharp increase from recent years.
CNN's Manu Raju contributed to this report.