The leading U.S. congressional committee looking at Russia's alleged meddling in the 2016 presidential race has endorsed the U.S. intelligence community's conclusions, saying that Russian propaganda efforts were much greater than previously reported.

The report, released on July 3 by the Senate Intelligence Committee, was endorsed by its Republican and Democratic leaders, serving as a subtle rebuke to President Donald Trump as he prepares for a momentous summit meeting next week with Russian leader Vladimir Putin.

Trump has repeatedly cast doubt on the conclusions of U.S. intelligence, which released a report in January 2017, just weeks before he took office.

That report said the President Putin had ordered a hacking-and-propaganda campaign aimed at swaying U.S. voters during the 2016 election.

Authored by the CIA, the FBI, and the National Security Agency, the report did not conclude whether the Kremlin had a clear preference for Trump or his Democratic rival, Hillary Clinton. But U.S. officials later said publicly that Moscow in fact did seek to support Trump.

"The committee concurs with intelligence and open-source assessments that this influence campaign was approved by President Putin," it said. "Further, a body of reporting, to include different intelligence disciplines, open-source reporting on Russian leadership policy preferences, and Russian media content, showed that Moscow sought to denigrate Secretary [of State] Clinton."

There was no immediate comment by the White House on the report, which was notably released on the eve of the U.S. Independence Day holiday.

Russia has repeatedly and vehemently denied the U.S. allegations.

The Intelligence Committee is one of three panels in Congress examining Russia's actions, as well as interactions between Russian officials and past and present Trump associates. While the other panels have been plagued by partisan infighting, the Intelligence Committee has been notably free of them.

The congressional investigations have overlapped in part with the criminal probe of Special Counsel Robert Mueller.

To date, Mueller has brought indictments against three companies and 20 people on various related charges. Those indicted include Trump’s first campaign manager, Paul Manafort, and Trump’s first national security adviser, Michael Flynn.

One of the companies indicted is the St. Petersburg-based Internet Research Agency, known informally as the Russian "troll factory."

The committee report noted that the January 2017 intelligence report mentioned the activities of the Internet Research Agency, which among things used social media to create fake profiles and cause discord and confusion.

However, it said, "the committee's investigation has exposed a far more extensive Russian effort to manipulate social-media outlets to sow discord and to interfere in the 2016 election and American society."

Trump and Putin are scheduled to meet for a summit in Helsinki, Finland, on July 16.

​Trump administration officials, including Secretary of State Mike Pompeo, have said Trump will raise the issue of election meddling with Putin, though Trump’s own recent comments make it unclear if that will happen.

Trump's longtime personal lawyer, Michael Cohen, who faces possible criminal charges in an unrelated case, said earlier this week that he also supported the intelligence findings.

"Simply accepting the denial of [Russian Vladimir Putin] is unsustainable. I respect our nation's intelligence agencies' unanimous conclusions," he said.