The Department of Energy has told the White House that without another $250 million in fiscal 1981, it will not be able to build all the nuclear weapons that President Carter says he wants, according to informed sources.

If it does not get the funds, sources said, the Energy Department may be forced next year to cut either domestic energy programs or some weapons building.

Last year, when the weapons building program ran short of money, department officials cut back on some solar research and delayed a start on initial production procurement for a new eight-inch nuclear artillery shell.

Yesterday, the Energy Department official in charge of the warhead building program, Assistant Secretary Duane Sewell, told a closed session of the House Armed Services Committee that the White House had not yet approved enough fiscal 1981 money to pay for the weapons proposed in the president's plans that were approved last November.

Half of the $250 million DOE sought was to pay for rising costs of weapons production; the other half was to go for more special nuclear materials.

Sewell told the committee the Office of Management and Budget so far had approved only $90 million for inflation and nothing for production of materials.

That line of testimony fell on sympathetic ears, because the committee has long been critical of what it has called the Carter administration's limited funding of the nuclear weapons program.

The situation in which nuclear warhead production must compete with domestic energy programs for the same funds arises from the fact that as heir to the old Atomic Energy Commission, the Energy Department has also become the home of the nation's nuclear weapons development and production program.

The fund competition within DOE has been exacerbated by the start of the country's first major nuclear warhead building program in 20 years and the larger-than-anticipated inflation rate.

Another factor has been the Pentagon's newly projected long-term warhead needs which, if actually met, would require additional production of costly nuclear materials such as plutonium and tritium.

Energy officials, needing funds to try to ease the nation's fuel problems, privately say that the Pentagon is proposing to buy more nuclear weapons that it needs because it doesn't have to pay for the warheads.

"The Defense Department gives orders for warheads," one DOE official said recently, "but they don't have to pay for them. We are the ones who have to trade them off against civilian requirements."

Earlier this year, then-undersecretary of energy John Deutch sent a letter to the OMB suggesting that his department's nuclear weapons program should be financed separately from the domestic energy program. In effect he wanted two separate budgets for DOE.

Deutch also proposed that when additional funds were needed for warheads, that money be taken away from other military programs -- not from energy programs.

"If that change were made," a DOE official said, "Defense would buy fewer weapons."

So far there has been no OMB reply to the Deutch letter.One OMB official said yesterday that doubted any change such as that proposed by Deutch would be made.

Deutch "proposed some uniqueness in the DOE-DOD situation that does not exist," the official said. "We have the same situation between [the National Aeronautics and Space Administration] and DOD in the space shuttle program."

In an opening statement read to yesterday's hearing, before the session was closed to the public, Armed Services Chairman Melvin Price (D-Ill.) said that "without corrective action," plans for building new cruise missiles, land-based ICBMs, submarine-based strategic missiles and tactical nuclear systems "may well be out of balance with the means to produce warheads."

At another point, the Price statement called the nation's nuclear weapons building complex "old and, in many cases, decrepit. . . ."

Yesterday's session was called to give committee members ammunition to take to the House floor next week in justification of additional funds they put into the DOE fiscal 1981 national defense authorization bill.