A memo obtained by the Financial Times says the U.S. military effort in Libya is costing hundred of millions of dollars more than first estimated.

The Pentagon memo, which the newspaper says was given to some U.S. lawmakers, says the military is spending $2 million a day on air strikes, refueling operations and intelligence gathering missions. That adds up to a cost of $60 million a month.

Earlier estimates from the Defense Department said the U.S. was spending about $40 million a month on its Libyan operations.

The Financial Times says U.S. military operations in Libya could cost Washington almost $300 million more than the Pentagon anticipated.

The increased costs are a concern for the U.S. military because the money comes from its normal budget. Funding for the U.S. military efforts in Afghanistan and Iraq come from separate, supplemental budgets.

NATO has been leading the air campaign against the forces of Libyan leader Moammar Ghadhafi. Earlier this week, outgoing U.S. Defense Secretary Robert Gates urged five key military allies to assume a greater role in the effort.

Last month, Gates said the total cost for U.S. operations in Libya had reached $750 million.