NATO Ministers Agree Strikes at Bosnia Serbs a Failure : Balkans: They vow grudgingly to step up air attacks to protect trapped U.N. peacekeepers.

NATO defense ministers agreed Thursday that their strategy of tit-for-tat air strikes in Bosnia-Herzegovina has been a failure, but the Western allies remained at odds over how much tougher they should get with defiant Bosnian Serbs.

Conceding that NATO’s credibility has been damaged by flagrant and unpunished violations of alliance edicts, the defense ministers vowed to escalate the use of air power to protect U.N. troops trapped between the warring factions without any authority to intervene.

But even their promise to make air strikes “proportionate, robust and effective” came grudgingly from countries with soldiers deployed in Bosnia as part of the beleaguered U.N. Protection Force.

British Defense Minister Malcolm Rifkind limited British support for intensified bombing runs to deterring attacks on U.N. troops, rather than as a means of protecting designated “safe havens” for Bosnian civilians or to enforce NATO-proclaimed weapons exclusion zones.

Asked if North Atlantic Treaty Organization ministers had worked out a plan for escalating air strikes, Rifkind said they had but added: “We don’t want to see that, and I hope that doesn’t happen. And it won’t happen if Bosnian Serbs do not provoke U.N. forces.”

French Defense Minister Francois Leotard described the firmer resolve to respond to Bosnian Serb provocations as “the price to pay” for getting the United States to back off from plans to unilaterally breach a U.N. arms embargo that has hampered only the Bosnian government forces.

Upon arrival here for a two-day NATO strategy session, U.S. Defense Secretary William J. Perry had pushed for broader use of air power to compel rebel gunmen to accept an internationally mediated peace plan.

All NATO countries with troops in Bosnia rejected any use of force with such political aims, sources involved in the closed-door talks reported. But they said the 16 defense ministers had agreed that the symbolic strikes launched so far had been too timid.

“NATO’s credibility is at issue here,” a senior U.S. official said. “We would like to see air power, when it is used, used in a robust way.”

The official criticized a Sept. 22 NATO response to a Bosnian Serb attack on French peacekeepers as “an effort to strike a derelict tank that didn’t impress anybody.”

A British official said Perry pushed for bombing rebel supply lines and ammunition depots as well as tanks and heavy weaponry used to attack U.N. peacekeepers.

But the tough talk from the U.S. delegation only highlighted the crux of the intra-NATO conflict, which is that member states with peacekeeping troops in Bosnia are less willing than Washington to support uses of force likely to anger the dominant Serbs and expose their forces to retaliation.

Britain, France, Canada, the Netherlands and Spain--all NATO members--provide the bulk of the 20,000-plus peacekeeping force in Bosnia.

Bosnian Serbs have intensified their defiance of NATO and the U.N. mission since the latest “pinprick” air strike last week.

Humanitarian aid convoys and the airlift of food into Sarajevo have been suspended because of rebel threats to fire on them, and attacks on the six purportedly U.N.-protected areas have been daily routine for months.

In addition to the rift between the United States and its allies, the verbal grappling session also confirmed disputes between NATO and the U.N. Protection Force that the allies have sought to play down.

“We’ve had this problem for 18 months. There is always a gap between the political will in the capitals and the generals” from NATO countries serving with the U.N. mission, a senior French military official said.

The defense ministers, who meet again today, plan to urge U.N. Secretary General Boutros Boutros-Ghali to pressure U.N. commanders in the Balkan war zones to act more aggressively to enforce the NATO exclusion zones and a resolution threatening air strikes if Bosnian Serbs persist with the strangulation of Sarajevo by cutting off water, electricity and gas to the Bosnian capital.

But a U.S. official conceded there had been problems in getting “individual allied countries to make clear to the United Nations what they want.”