House Intelligence Committee Chairman Adam Schiff, D-Calif., said Sunday that Congress is "running out of time" to have former special counsel Robert Mueller testify, adding that he hopes a "final conclusion" is reached on his possible testimony "this week."

"We have been in private discussions with the special counsel's office," Schiff told CNN's "State of the Union." "It is not clear that he will refuse to come in voluntarily; we are negotiating what the conditions of that appearance might be. But yes, we are running out of time."

"I hope that we'll reach that decision this week because we want to have him come in during July and I think that's going to be the case ... whether it is voluntary or involuntary by subpoena," Schiff added. He told CNN last week that he wants Mueller to testify before the August recess.

Last month, Mueller said his 448-page report on Russian electoral meddling, whether the Trump campaign conspired with Russian officials and whether Trump obstructed justice "speaks for itself," adding that if he did testify to Congress, he wouldn't provide any information "beyond what is already public."

"The report is my testimony," Mueller said. "We chose those words carefully and the work speaks for itself."

Trump has repeatedly said calls for Mueller to testify amount to a "do-over" of the special counsel's report, which he has incorrectly claimed exonerates him of wrongdoing.

"I don’t know why the Radical Left Democrats want Bob Mueller to testify when he just issued a 40 Million Dollar Report that states, loud & clear & for all to hear, No Collusion and No Obstruction (how do you Obstruct a NO crime?)" Trump tweeted last month. "Dems are just looking for trouble and a Do-Over!"

Mueller's report did not come to a traditional prosecutorial decision on whether Trump obstructed justice.

"If we had had confidence that he clearly did not commit a crime we would have said so," Mueller said last month. "We did not, however, make a determination to whether the president did commit a crime."