AP
"The President has made it clear: we're not going to negotiate over the debt limit," Lew said.
That has been a sticking point for President Barack Obama since the summer of 2011, when negotiations over the debt ceiling led to a near breach and played a part in a downgrade of the nation's credit rating. During the fiscal cliff debate late last year, Obama said he wouldn't be negotiating over the debt limit.
Lew drew a contrast between the upcoming fiscal debates, which also includes the need to pass a continuing-resolution bill to fund the government after Sept. 30. In another familiar line, he cast the debt-limit debate as one over bills that Congress has already racked up.
"The debt limit is just different. ... These are old bills that have to be paid," he said.
Lew wrote a letter to Congressional leaders on Monday outlining a mid-October deadline for raising the nation's debt limit.
"It used to be that the debt limit was used as a deadline to force action to come together," Lew said.