AR RUQ'I, Saudi Arabia (AP) _ Two 19-year-old Saudi soldiers, Hassan and Saad, peer through slits in their foxhole trying to catch a glimpse of Iraqi troop movements across the no man's land from this border outpost.

If war breaks out, there is a good chance these two teen-agers will be in the thick of it almost immediately.

They form the frontline defense, less than a mile from Kuwait, where thousands of Iraqi troops are dug in. A 6-foot-high wall, automatic rifles and a Sherman cannon would provide little defense against an Iraqi tank attack.

Now that their foxhole is dug, Hassan and Saad find the waiting game tiring.

''Boring,'' says Hassan as he strains to see the Iraqis.

As the world agonizes over how to drive the Iraqis out of Kuwait, Hassan and Saad along with two dozen colleagues from the Saudi frontier force at a desolate desert post 20 miles to the rear have trouble keeping up with developments.

Here along the long border Saudi Arabia shares with Kuwait and Iraq, west of the huge oil fields near the Persian Gulf defended by the U.S. forces, is where the Arab multinational force has drawn its line in the sand.

More than 50,000 soldiers, part of the Joint Arab Forces, are deployed in positions behind the border. Joining the Saudis are troops from Egypt, Syria, Morocco and the smaller gulf nations.

The closest American troops are at least 100 miles away.

Saddam Hussein's Aug. 2 invasion of Kuwait has done little to change the typically slow pace of life at the checkpoint manned by Hassan and Saad and the larger border post of Ar Ruq'i.

The flat desert here is so barren, dusty, and dry that even shrubs won't grow and the ubiquitous Saudi camels are nowhere in sight. A car hulk is the only landmark in the scorching sand.

At the Ar Ruq'i post, members of the frontier force sit cross-legged on the floor inside a concrete building sipping tea. Huge posters of Dutch tulip are on the walls.

Visitors are rare because the area is restricted to the public without permission from the local emir, or mayor.

Refugees fleeing Kuwait in the first days after the invasion created an air of excitement, but that has stopped now.

''Right now, no Kuwaitis,'' said a frontier force captain at the post. A crackdown by Iraqi troops has slowed the flow of refugees.

The frontier forces and the emir's people know - and help - the Kuwaiti resistance, which operates out of a Saudi government-owned apartment complex 70 miles away.

A resistance leader, who asked to be referred to only as Sheik M., said its efforts are centering on bringing people out of Kuwait these days.

''We bring out the families. We make them safe, then the men go back to fight,'' Sheik M. said.

At Ar Ruq'i, Emir Sultan Abu Mohammed and his entourage have been sleeping at their concrete headquarters since the Iraqi invasion. In his carpeted office, the emir fiddles with his short-wave radio trying to get the latest news.

The emir's right-hand man is his son, Mohammed, who has left his wife and children in their house 10 miles away.

Although he lives in the office, Mohammed maintains a none-too-strenuous routine. In the evening, he and a few friends gather at a government guest house to eat a hearty chicken-and-rice meal, drink non-alcoholic beer and watch the local news on TV.

When Saddam's face flashes on the screen, one man, Abu Ali, spits at the screen.