UN observers pull troops and civilians back from the Kuwaiti border

The United Nations withdrew its civilian staff and a fifth of its peace-keeping troops from the border between Kuwait and Iraq yesterday amid growing signs of preparations by US troops for a military strike.

The Kuwait-Iraq Observer Mission (Unikom), which has monitored the border for the past dozen years, upgraded its alert status to "red" as senior officials conceded that chances of avoiding a conflict appeared to have disappeared. Raising the alert status meant that about 230 civilian staff and 150 Bangladeshi peace-keepers were sent back to the capital, Kuwait City, while the 195 military observers and the remaining 625 troops were told their patrols must be confined to daylight hours. A UN official said the civilians had been moved back from the border "for their own safety".

With the Security Council deliberating on a resolution from Britain and the US that would pave the way for military action, Unikom officials admit the alert status could be raised again soon, which would force the observers and peace-keepers to be withdrawn. Arrangements have already been made to move observers out of the region in the event of a war, with Westerners having been given visas for Italy and non-Westerners with Bangladeshi visas.

Observers said they had seen continuing activity by US troops in the so-called Demilitarised Zone (DMZ) in preparation for a northward move by troops, tanks and artillery. On Friday it was revealed that private contractors had been cutting holes – big enough to accommodate a tank – in the 125-mile fence that marks the border between Iraq and Kuwait. Yesterday it was reported that American troops had started dismantling sections of a sand ridge that also runs along the border.

It was also said that US troops had been seen moving in ready-made bridges that could be used by tanks or other armoured vehicles to cross defensive trenches that were dug by the Kuwaiti authorities in the southern part of the DMZ.

US forces have yet to comment on their activities in the DMZ. The zone, stretching six miles into Iraq and three miles into Kuwait, is only supposed to be entered by UN personnel as well as Kuwaiti and Iraqi border guards, carrying only handguns, in their respective zones. As such, any troops would be breaching the UN's rules.

The number of US and British forces in Kuwait is now close to 300,000, a figure that is considered to provide the Pentagon with the full range of tactical options. American forces include the "Screaming Eagles" – the 101st Airborne division, the 82nd Airborne and the 3rd Mechanised Infantry division, while Britain has dispatched 4,000 Royal Marines and special forces, 16 Air Assault Brigade, and the reinforced 7th Armoured Brigade – the "Desert Rats".

The red-alert status is the third highest level used by Unikom. If this was raised to the next level the peace-keepers would stop all operations. At stage five they would evacuate the country.