(CNN) Vice President Mike Pence urged special counsel Robert Mueller on Thursday to end his investigation into potential collusion between the Trump campaign and Russia during the 2016 election.

The vice president's comments to NBC News are his most direct yet in pressuring the special counsel to drop the investigation, which President Donald Trump has frequently referred to as a "witch hunt."

"Our administration has provided more than a million documents; we've fully cooperated in it, and in the interest of the country, I think it's time to wrap it up," Pence said in an interview.

Sens. Chuck Grassley and Lindsey Graham responded to Pence's remarks, both defending Mueller's process.

"That's not Vice President Mike Pence's decision to make," Graham, a South Carolina Republican, said. "I'm sure Mr. Mueller will wrap it up when it gets time to wrap it up. The only thing I can say is I haven't seen any evidence of collusion. Mr. Mueller has a good reputation, and we'll see what his report says and where he goes."

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