Story highlights Justice Department and JPMorgan reached tentative, $13 billion settlement last week

The deal covers the bank's mortgage securities practices

Sticking point involves liabilities associated with JPMorgan's purchase of failing Washington Mutual

JPMorgan finalizes portion of settlement with housing agency

The Justice Department and JPMorgan Chase are wrestling with whether some of the $13 billion tentative settlement covering JPMorgan's mortgage practices should come out of the government's pocket, a source familiar with the talks told CNN.

Lawyers for the two sides are continuing talks on some final sticking points in the settlement covering the bank's mortgage securities practices.

The outline of the deal was struck last Friday.

The biggest point of contention remaining is whether some of the settlement money covering mortgage securities sold by Washington Mutual, which was acquired by JPMorgan, could end up coming from the Federal Deposit Insurance Corporation (FDIC), the government-backed insurer of banking deposits, the source says.

When JPMorgan bought failing Washington Mutual from the government in 2008, the FDIC was stuck with some of its liabilities.

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The Justice Department insists on language in the settlement that would prohibit JPMorgan from making claims against the FDIC for some of the money it is going to have to pay.

On Friday, JPMorgan and the agency that oversees Fannie Mae and Freddie Mac concluded their portion of the broader settlement.

The bank agreed to pay $5.1 billion to the Federal Housing Finance Agency (FHFA) to cover alleged deceptive practices in sales of mortgage securities, including by Washington Mutual, to the government-backed housing finance giants.

The FHFA agreement doesn't include a prohibition on JPMorgan recovering money from the FDIC. Justice Department lawyers want it included in their final deal.

JPMorgan declined comment.