BRUSSELS, DEC. 2 -- Defense Secretary Frank C. Carlucci warned his European colleagues today that the United States cannot continue to pump more money into NATO defenses, despite heightened concerns among the allies over conventional forces.

Carlucci's tough budget talk came as the North Atlantic Treaty Organization's defense ministers firmly endorsed the pending superpower agreement to eliminate intermediate-range nuclear weapons.

The prospects of that agreement have drawn new attention to NATO's effort to modernize its conventional defenses.

The pending agreement on intermediate-range missiles, along with the financial difficulties of improving NATO's conventional forces, dominated the two-day NATO Defense Planning Committee meeting that ended here today.

Although the final communique stressed the need to improve conventional forces, Carlucci told reporters after the session, "I'm not going to make the claim there will {be} large-scale improvement in capability, given the constraint we all face."

NATO's secretary general, Lord Carrington, told reporters, "The U.S. is suffering increased financial difficulties and can't be expected to carry as large a share of the defense burden as in the past."

Carrington, noting that "there is nothing evasive" about Carlucci, said the U.S. defense secretary told his colleagues that "the facts of life are about the defense budget" in the United States.

Carlucci said he told the defense ministers that NATO would have to become more innovative in stretching its financial resources.

The defense ministers reiterated their earlier support for the pact between the Soviet Union and the United States to scrap all medium- and shorter-range nuclear missiles, noting in their official communique, "We welcome and fully support the agreement."

The defense group also urged additional movement in talks between NATO and the Warsaw Pact on an arms control agreement for conventional forces.

Although some European leaders said they expect the treaty on intermediate-range missiles to create an atmosphere that could spur the conventional arms talks, Carrington said he believes any final agreement is still several years away.

The NATO allies are not yet unified on their own proposal for a conventional arms agreement.