PRISTINA, Sept 5 (Reuters) -- It was definitely not life in the fast lane on the Kosovo-Macedonia border at the weekend.

The mother of all traffic jams stalled military and civilian vehicles in queues that stretched for miles (km) on both sides of the main border crossing north of the Macedonian capital of Skopje on Saturday.

"The only way to deal with this is to bring in the army," muttered one U.S. sergeant, a member of the NATO-led KFOR peacekeeping force in Kosovo.

"But we are the army and we've been here stuck here for hours just like everybody else. Nobody seems to know what to do. Can't go forward, can't go back. Nobody's in charge."

The soldier, sweltering in his flak jacket and battle helmet, was looking for a place to relieve himself along the narrow, two-lane road.

Steep embankments, thick with brush, provided plenty of cover on either side of the road. But with land mines an ever-present danger along the border many people were using the tarmac as their latrine.

As far as the eye could see in both directions massive military transporters stood nose-to-tail, intermixed with Yugos and ancient Mercedes crammed with civilian passengers.

Many of the transporters were being driven by American civilians, contract employees building a huge U.S. base, known as Camp Bondsteel, in southeastern Kosovo.

Clad in blue jeans and T-shirts, aviator sunglasses wrapped around their suntanned faces, the men stood in small groups cursing, joking and spitting tobacco juice onto the dirt verge.

American country music blared from the tape decks in their rigs, mixing with traditional Macedonian folk tunes issuing from convoys of trucks out of Skopje loaded down with relief supplies for Kosovo.

On the Kosovo side of the border, aid workers and United Nations bureaucrats trying to escape to Skopje for the weekend in smart four-wheel drive vehicles were bogged down.

On the Macedonian side, idling buses packed with ethnic Albanian refugees headed home to Kosovo were disgorging their passengers, who immediately hired young boys with wheelbarrows to push their string-tied luggage up to the border crossing.

Two British Ghurka soldiers sat cross-legged on the bonnet of their Land Rover, chatting in Nepalese, seemingly oblivious to the chaos, as French, American and German KFOR officers wandered impotently among the vehicles.

Rising above the tangle of traffic and the frayed tempers was a thick, headache-inducing cloud of diesel fumes.

At the Macedonian immigration station an official explained that the problem was on the Kosovo side of the border:

"There is no discipline over there. Primitive people, primitive place," he said.

On the Kosovo side a Dutch KFOR officer whispered conspiratorially: "It's like this every day. The problem is on the Macedonian side. There's no proper traffic control."

Tempting though it might be to see the border blockage as a Balkan quagmire metaphor, the problem seemed self-induced.

An American KFOR military convoy heading north into Kosovo had come up on the tail end of the usual queue formed at the border and, instead of waiting, had swung out into the oncoming lane in an attempt to bypass the delay.

But as the American convoy neared the crossing point it met a French military convoy headed south.

Seeing the Americans pull out into the oncoming lane, other northbound vehicles jumped in behind them, making it impossible for the convoy to reverse. The French were similarly boxed.

A bypass to shunt KFOR traffic around the crossing is in the works but construction could take several more weeks.