U.S. Trade Representative William E. Brock, saying he was "bone tired" and "fed up" with nations balking at recently negotiated export subsidy reductions, warned yesterday that the administration could fight back with its own, even higher subsidies.

Brock, known for more moderate tones when discussing trade issues, said his tough talk came "out of intense frustration" with nations that have put off for about three weeks signing the agreement for further lowering export subsidy levels. His remarks were made at an economic conference and during an interview.

"We've tried very hard to negotiate export subsidies," Brock said. "But the European Community is unable to agree on it yet."

"I am so fed up with our inability to eliminate this practice," Brock continued during an interview. "I personally would advocate the use of a 2-by-4 in whatever fashion we could get" to force the nations to agree on the subsidy levels. "I am pretty well fed up."

There was no immediate comment yesterday from European officials on Brock's remarks.

The administration for months has slowly negotiated reductions in export subsidies and has made the elimination of all subsidies one of its goals.

Such subsidies have given foreign firms advantages in contract bidding. For example, the administration is looking into allegations that a nearly $700 million contract to a Canadian company for providing subway cars to New York's Metropolitan Transportation Authority may have been subsidized at an interest rate below that already agreed upon by the industrial nations.

"I'm personally willing to take a look at all the proposals to get competitive," Brock said, including establishing a "war chest" of money for export financing to compete with other countries. He said that also under consideration is increasing lending authority for the Export-Import Bank and focusing loan programs on "a few selective areas."

Brock wouldn't say which countries were giving him the most trouble. But sources said France, which has been accused of providing heavy subsidies, instigated pushing back the date for agreement.

Brock said he didn't think postponing the signing until June 15 was a delaying tactic, but that the countries just couldn't come to any agreement.