President Trump’s longtime lawyer Michael Cohen will testify before a Senate panel investigating Russian interference in the 2016 election on Tuesday, NBC reported on Sunday.

Cohen, a lawyer for the Trump Organization, has admitted that he reached out during the campaign to a spokesman for Russian President Vladimir Putin for help on a real estate project in Moscow but the aide never got back to him and the development never got off the ground.

Last month, his lawyer sent a letter to the House Intelligence Committee, denying claims that Cohen colluded with Moscow to meddle in the election, allegations made in a 35-page dossier that surfaced earlier this year.

“We have not uncovered a single document that would in any way corroborate the dossier’s allegations regarding Mr. Cohen, nor do we believe that any such document exists,”​ his lawyer,​ Stephen M. Ryan, wrote in the eight-page letter.​

​A number of congressional panels, as well as the FBI and special counsel Robert Mueller, are probing Russian involvement in the presidential election and whether there was any coordination with Trump campaign associates. ​