U.S., Allies Start to Boost Bosnia Force : Balkans: Defense Secretary Perry says he may send more planes to help protect U.N. troops. He predicts Serbian harassment will intensify.

The United States and its NATO allies Saturday began carrying out their new plan for beefing up protection of U.N. peacekeeping forces in Bosnia-Herzegovina, and there were indications the additional troops and equipment could be in place within two weeks.

U.S. Defense Secretary William J. Perry, speaking with reporters after a meeting in Brussels at which NATO defense ministers formally endorsed the 10,000-member British-French rapid-reaction force, said he may send more U.S. escort planes to Italy to help jam or destroy Serbian missile radar.

But almost as soon as the rapid-reaction force is in place, he predicted, it will be “tested” by the Serbs, who are likely to intensify harassment of U.N. forces in a bid to jolt the allies’ confidence.

“What happens after that really depends on the dynamics of how effective the rapid-reaction force is and how the Bosnian Serbs react to that,” Perry said. “And that’s too difficult to predict at this stage.”

Serbian nationalists have seized hundreds of U.N. peacekeepers over the past weeks. Most have been freed, but about 145 are still held hostage, and officials said the allies hope to step up pressure on the Serbs to win their release.

Perry also decried last week’s House vote to lift the arms embargo against the Bosnian Muslims, saying that would be “a particularly bad idea now” because it would pull the rug out from under the U.N. peacekeeping effort just when the new allied plan is going into effect.

He said that, if the United States broke the embargo, the allies would withdraw their peacekeeping forces, the rebel Serbs would resume their attacks and there would be a sharply increased risk that the war would spread and possibly involve Greece, Turkey and the Serbian province Kosovo.

That, in turn, would force the United States to send a massive number of troops, first to help evacuate the U.N. peacekeeping forces and later, perhaps, to keep the fighting from spreading across the rest of Europe, Perry said.

“The U.S. should not be the cause of withdrawing [the U.N. peacekeeping forces], which would be the case if we went through unilateral lift” of the embargo, Perry said. “I do not believe that those who are advocating unilateral lift have thought through the consequences.”

Perry said he is confident the new allied rapid-reaction force “has a good chance of success.”

Even so, U.S. and allied officials conceded last week that some daunting problems remain--including questions about when U.N. officials may veto proposed allied military measures.

The rapid-reaction force, for example, technically will be subject to the orders of U.N. military commanders in Bosnia but will not require the approval of Yasushi Akashi, the organization’s civilian envoy, who has blocked NATO-proposed air strikes before.

At the same time, the allies still will have to obtain U.N. approval before they can launch preemptive strikes to knock out rebel Serb radar and missile batteries, such as the one that on June 2 downed the F-16 piloted by U.S. Air Force Capt. Scott F. O’Grady.

U.S. and NATO commanders also are re-evaluating whether the allies have enough escort aircraft--such as F-4G Wild Weasels, which can fire radar-homing missiles, and EF-111 planes with radar-jamming gear--to protect F-16 fighters from Serbian air defenses.

Perry said he expects to receive a recommendation in “a day or two” from U.S. Adm. Leighton Smith, commander of NATO forces in southern Europe, on how many more planes might be needed. The United States has only six EF-111s at Aviano Air Base in Italy, where Bosnian patrols are stationed.

The secretary also raised the possibility that the Pentagon might reconsider a recent Defense Department decision to retire many of its EF-111s and F-4Gs, which were supposed to have been phased out over the next two years because they no longer were needed.

In criticizing the House demand that the Administration lift the arms embargo, Perry warned that, contrary to suggestions by those who advocate such a move, getting tanks and artillery to the Bosnian Muslims would not be an easy job.

Not only would shipping the weapons to the Muslims require the consent of Croatia, but the United States would be obliged to train the Muslims to use the weapons, which easily could take months.

“It’s not at all clear that simply delivering tanks and artillery and saying ‘Lots of luck’ is going to be very effective,” he said.