Proposed rules of engagement for an expanded UN force in southern Lebanon would allow troops to open fire in self-defense, protect civilians and back up the Lebanese army in preventing foreign forces or arms from crossing the border, according to a UN document obtained Tuesday by The Associated Press.

The 20-page draft was circulated to potential troop-contributing countries last week by the UN Department of Peacekeeping Operations, which is trying to get an additional 3,500 troops on the ground by the end of next week to strengthen the 2,000 overstretched UN peacekeepers already there.

The rules of engagement for the expanded force - which is authorized to grow to 15,000 - have held back some potential troop contributors - notably France - because of concerns that their soldiers would be required to disarm Hizbullah, which has controlled southern Lebanon.

Some countries have also been concerned that the rules would be overly restrictive, all but preventing commanders from making quick decisions - including using force if needed.

While remaining "predominantly defensive in nature," the draft rules allow for the use of "deadly force" and offensive action, if necessary, to ensure implementation of the August 11 UN resolution that led to the fragile cessation of hostilities between Israel and Hizbullah.

Although there is no authorization in the Security Council mandate or the rules of engagement to disarm Hizbullah, the rules are sufficiently robust to put the UN potentially in conflict with armed groups violating the cease-fire or the arms embargo - including Hizbullah.

The rules would also give the UN commander on the ground wide-ranging authority to react.

The UN force is also authorized to help the Lebanese army establish a buffer zone in the south and secure its borders to prevent arms smuggling.

The draft rules of engagement would allow "use of force, up to and including deadly force, while assisting the government of Lebanon, at its request to secure its borders and other points of entry to prevent the entry into Lebanon, without its consent, of foreign forces, arms or related material."

The rules would also authorize lethal force to "protect civilians under imminent threat of violence, when competent local authorities are unavailable or unable to render immediate assistance." Force could also be used "to ensure the security and freedom of movement of UN personnel and humanitarian workers."