WASHINGTON — Treasury Secretary Jacob Lew has told Congress that the government will run out of money to pay its bills in mid-October unless lawmakers raise the country’s borrowing limit, which is capped at $16.7 trillion.

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FILE - In this April 8, 2013, file photo U.S. Treasury Secretary Jacob Lew listens to a question during a media conference at EU headquarters in Brussels. Congress needs to raise the debt limit and take away the "cloud of uncertainty" about the nation's ability to pay its bills, Lew said in an interview broadcast Sunday, July 28, 2013. "The fight over the debt limit in 2011 hurt the economy... Congress needs to do its job. It needs to finish its work on appropriation bills. It needs to pass a debt limit," he said. AP

Lew said in a letter to Speaker John Boehner released Monday that the government is running out of accounting maneuvers it has used to avoid hitting the borrowing limit. He pressed Congress to act so Treasury can keep paying the government’s bills.

Lew said it’s impossible for Treasury to predict exactly when borrowing limit will be reached. But he warns that if action isn’t taken soon, the government could be left with $50 billion in cash by mid-October. He says that wouldn’t be enough to cover Social Security payments, military personnel salaries, Medicare and other programs for an “extended period.”

Lew told CNBC in a Tuesday morning interview that there cannot be any question that the United States is a country that pays its bills.

“It’s not as if we get to go back and undo the commitments we made,” he said. “These are old bills that have to be paid.”

Earlier this year, Congress temporarily suspended the borrowing limit so lawmakers could focus on other budget debates. Treasury has kept the government operating for several months through its bookkeeping maneuvers. A smaller deficit this year has also helped.

The government is spending more than it takes in, running up annual deficits in excess of $1 trillion in each of the past four budget years. It has been borrowing the difference to meet its obligations.

Republicans want to reduce future deficits by cutting back sharply on spending. Democrats have proposed a mix of spending cuts and tax increases, which Republicans strongly oppose. The issue awaits resolution when lawmakers return from the recess.

Congress last passed legislation to increase the borrowing limit in the summer of 2011 after a months-long negotiation between President Barack Obama and top lawmakers like Boehner. Republicans forced Obama to accept about $2 trillion in spending cuts over the coming decade in exchange for a like-sized increase in the borrowing limit.

Obama says he won’t negotiate on the debt limit this time around and says Congress should fund the spending it has previously approved.

Many Republicans want to use upcoming budget deadlines to mount an assault on Obama’s signature health care law. Top House Republicans could use the borrowing limit measure as a way to derail “Obamacare,” though the White House and top Senate Democrats say that’s a nonstarter.

Lew told CNBC the administration would not accept a delay or defunding of parts of the law, which aims to help millions of uninsured people gain health insurance coverage. The law calls for the expansion of the state-federal Medicaid program starting next year in many states and for income-based subsidies to help people buy individual policies.

__ Associated Press writers Andrew Taylor in Washington and Tom Murphy in Indianapolis contributed to this report.