Leadership in both chambers is still hoping to be able to negotiate a larger deal on the defense and nondefense budget caps before they leave for the August recess, into which they could fold a debt ceiling increase.

Merging the two items would let them condense the number of politically tough votes. But the budget and the debt ceiling are on two different timelines. While Congress is likely to have to increase the debt ceiling in weeks, they have until January to pass a budget and avoid across-the-board cuts known as sequestration.

Mnuchin's letter to Pelosi comes after the two spoke on the phone multiple times this week as they tried to negotiate a larger budget deal. They're expected to talk again on Friday.

Pelosi told reporters on Thursday that Congress should act on a budget caps deal to raise the debt limit in the next few weeks."I am personally convinced that we should act on the caps and the debt ceiling,” Pelosi told reporters, “prior to recess.”