The Russian lawyer who met with Donald Trump Jr. during the 2016 campaign while promising damaging information on Hillary Clinton offered President Trump's eldest son opposition research created by Fusion GPS - the firm behind the unverified Trump/Russia dossier, according to Reuters.

Natalia Veselnitskaya's negative information related to Hillary Clinton and Clinton Foundation donors was reportedly created by Fusion GPS.

The White House has repeatedly attacked Fusion GPS for its role in the dossier of explosive allegations about Trump's ties to Russia.

The research obtained by Veselnitskaya was created through an unrelated Fusion GPS investigation, according to Reuters.

The Trump administration and Republicans have attacked the Democratic National Committee and the Clinton campaign for funding Fusion GPS's research after the project was abandoned by GOP backers during the Republican primary.

Glenn Simpson, one of the firm's founders, met with Veselnitskaya before and after her 2016 meeting at Trump Tower with Trump Jr., Paul Manafort and Jared Kushner, according to the report. But Simpson was unaware that the meeting had taken place, according to a source familiar with his testimony in the special counsel probe.

In July, Trump Jr. released a chain of emails revealing that an associate had offered to set up the meeting between him and Veselnitskaya, explaining the information she could provide "would incriminate Hillary and her dealings with Russia and would be very useful to your father," and was "very high level and sensitive information but is part of Russia and its government's support for Mr. Trump."

"If it's what you say I love it especially later in the summer," Trump Jr. wrote back in an email.

Robert Mueller's special counsel office has been looking into both the Fusion GPS dossier as well as the meeting between Trump Jr. and Veselnitskaya at Trump Tower as part of the investigation into possible collusion between the Trump campaign and Russia.