"I'll simply say all options are on the table, that's all I'm going to say publicly," Nadler told reports on Tuesday when asked about possibly supporting impeachment proceedings.
Nadler was joined by other Democratic leaders after the House of Representatives passed a resolution authorizing committees to take legal action against against Attorney General William Barr, former White House Counsel Don McGahn and other Trump administration officials who may be defying congressional subpoenas to be questioned.
The House of Representatives voted 229-191 on Tuesday to let committees go to court to enforce the subpoenas.
Russia has repeatedly denied any claims of interference in the US political system, saying the allegations were made up to excuse the election loss of Trump's 2016 opponent, as well as deflect public attention from actual instances of election fraud and corruption.