Article snippet: Chuck Grassley. Representatives for both Trump Jr. and Manafort did not respond to requests for comment from ABC but previously said they are cooperating with the Congressional investigations. The announcement comes a day after senators threatened to subpoena the pair in pursuit of their investigation into Russian Dianne Feinstein, D-Calif., had expressed confidence on Thursday in achieving cooperation with the president's son and former campaign chair. “I’m not concerned, because if they don’t they will be subpoenaed," said Feinstein. On Wednesday, the committee invited the men -- who have come under scrutiny for their attendance at a June 2016 meeting at Trump Tower in which Trump Jr. believed they would receive incriminating information about Hillary Clinton -- to appear at a hearing next week and turn over documents related to their contacts with Russian nationals. They will not appear at Wednesday's session in light of their willingness to cooperate, according to an aide to Feinstein. Glenn Simpson, founder of Fusion GPS, a research firm hired by Trump political opponents to investigate the GOP nominee's Russia ties, was also invited to next week's hearing, but declined, according to the statement from Grassley's office. "A subpoena has been issued to compel his attendance," the statement said. "Simpson's attorney has asserted that his client will invoke First and Fifth Amendment rights in response to the subpoena," continued the statement. W... Link to the full article to read more