SKOPJE Macedonia accused ethnic Albanian rebels of new truce violations on Friday as NATO nations meeting in Brussels looked likely to put off a decision on whether to risk sending a 3,500-strong force to implement a peace plan.

A British-led vanguard of about 400 troops was set to start arriving in Skopje on Friday to pave the way for the bigger force when, or if, NATO gives the green light to send a mission to collect guerrilla arms and try to prevent a fifth Balkan War.

NATO has said that a durable cease-fire is a key condition for sending any more troops for "operation essential harvest", which would be the alliance's third mission to the Balkans alongside peacekeeping operations in Bosnia and Kosovo.

The Macedonian government said rebels flouted the truce on both major fronts overnight after a policeman was shot dead in the northwestern town of Tetovo, apparently by a rebel sniper, the worst setback so far to a ragged truce declared on Sunday.

Rebels said the Macedonians started the fighting. NATO ambassadors began talks in Brussels on Friday about whether conditions were right for full deployment. But diplomats said many countries were unsettled by the cease-fire violations and were likely to decide next week on whether to go ahead.

In Macedonia, Defense Ministry spokesman Marijan Gurovski told Reuters: "We were fired at late on Thursday from the villages of Nikustak and Vistica toward our positions in Umin Dol."

*********Reconnaissance Planes *************

To the west of the capital Skopje, army planes were flying reconnaissance missions over the tetovo region on Friday.

Gurovski denied rebel charges of bombing raids in the northern village of Radusa.

The state news agency MIA said "Albanian terrorists" had used snipers, mortars and heavy machine guns from a stronghold at Sipkovica and Gajre west of Tetovo during the night.

Amid the messy cease-fire, a first group of 16 Czech paratroopers in the mostly British advance guard was set to arrive at Skopje airport at about 1200 GMT.

The first planeload of 40 british soldiers would follow at about 1830 GMT and British spokesman Alexander Dick said the rest of the 400-strong vanguard would fly in over the weekend to set up a headquarters.

"Over the coming days, we will need to assess very carefully the current cease-fire," he told a news conference. The vanguard would contact all sides and would also try to assess the sincerity of rebel pledges to hand their weapons to nato troops.

If deployed, the NATO force is meant to stay for a lightning 30-day mission to collect weapons to be surrendered voluntarily by rebels at the end of a six-month conflict in return for political reforms favoring the one-third ethnic albanian minority.

Separately, the ****Washington Post**** said the U.S. government planned to finance a media blitz in Macedonia in a campaign for parliamentary passage of a peace agreement signed by the leaders of Macedonian and ethnic Albanian political parties on Monday.

NATO officials say the alliance faces a dilemma. By delaying too long in sending any troops, the Western-brokered peace deal may Yollapse. yet by arriving too quickly, NATO risks getting caught in crossfire.

The rebels' political chief told Reuters the 30-day NATO mission would be too short but insisted the rebels were committed to peace.

"Thirty days is not enough time. We asked for a much longer deployment," Ali Ahmeti said in a rare interview on Thursday in the guerrillas' mountain stronghold of Sipkovica.