AS the United States and its European allies squabble over how to follow through on their latest Bosnian ultimatum, the Bosnian Serbs are once again calling their bluff.
After telling the Bosnian Serbs they would face airstrikes if they attacked the UN ''safe area'' of Gorazde, the US, France, and Britain began the week divided over how to implement the threat. Nor could they agree on whether the warning applied to assaults on other Muslim enclaves under nominal UN protection.
And in another possible sign of disunity, France may have taken matters into its own hands and unilaterally hit back against the Bosnian Serbs to avenge the latest killings of French UN troops.
For his part, Gen. Ratko Mladic, the Bosnian Serb military chief, did what he has done so well before: exploited the now-familiar pattern of division and indecision that has stymied Western policies on Bosnia since the war erupted more than three years ago. Warned not to hit Gorazde, General Mladic intensified attacks on two other Bosnian government enclaves: Sarajevo and Cazinska Krajina, a northwestern region dubbed the ''Bihac Pocket'' after its main town.
''The Serbs are always trying to stay a step ahead and outthink the allies as to what's next,'' says a senior US military official. ''When we ramp up the pressure, they are like a tube of grease that squirts out in another direction.''
Just how the US and its allies will handle the latest developments remains uncertain. ''The situation is still evolving,'' says another US military official.
The new Western disagreements follow a conference on Bosnia held July 21 in London by the US, Britain, France, Russia, and 12 other nations in response to the July 11 Bosnian Serb conquest of the eastern UN ''safe area'' of Srebrenica. Ignoring an assault of a second enclave, Zepa, the participants - save Russia - warned the Bosnian Serbs that they would face NATO airstrikes if they moved on Gorazde. The eastern town's 70,000 Muslim residents and refugees have been besieged, bombed, and periodically deprived of food supplies for past three years.
But differences resurfaced after the conference, when planners at the Brussels-based North Atlantic Treaty Organization began working out the details of the airstrikes. The thorniest issue concerned the question of who would authorize what US Defense Secretary William Perry described as a ''major air campaign.''
The US opposes the current ''duel key'' arrangement by which UN military commanders in Bosnia obtain approval for NATO planes to repulse attacks on their troops. The US views the system as time-consuming and convoluted because it runs from Sarajevo to Yasushi Akashi, the Zagreb-based civilian chief of the UN Protection Force, to UN Secretary-General Boutros Boutros-Ghali in New York.
Washington wants the UN civilians cut out and decisions vested in Gen. Rupert Smith, the British UN commander in Sarajevo, and US Adm. Leighton Smith, NATO chief for southern Europe. A US official says France and Britain want that authority given to General Smith's military superior in Zagreb, French UN Gen. Bernard Janvier.
The UN insists that airstrike approval remains with Mr. Boutros-Ghali. The US counters that the London conference agreed that the power to summon the 200-odd plane NATO force deployed on aircraft carriers and in Italy be given to the military. ''We are quite clear that a change has been made,'' says State Department spokesman Nicholas Burns.
Another disagreement centered on claims by Clinton administration officials that the airstrike threat is as applicable to Bosnian Serb attacks on Sarajevo and Bihac as it is to Gorazde. ''If it becomes necessary to extend additional authority to protect those 'safe areas' we would certainly do that,'' says Mr. Perry. US officials say the British and French were resisting that interpretation.
A French newspaper, meanwhile, reported on July 24 that without consulting its allies, France struck back at the Bosnian Serbs on July 23 for an attack on a UN base in Sarajevo that killed two French UN soldiers. The Paris-based daily, Liberation, said a French Mirage 2000-D jet flying from a base in France dropped a laser-guided bomb on a house in Pale belonging to an associate of Bosnian Serb leader Radovan Karadzic. Paris denied the report, although French President Jacques Chirac told reporters on July 23 while on a visit to Senegal that he had ordered a ''counterstrike'' to avenge the deaths of the French soldiers.
Reviewing the current state of play in Bosnia, one official says: ''This shows how little was done in London. It seems like a huge farce to anybody looking at it from the outside.''