GENEVA - World powers share a "profound concern" that Syria is descending into civil war but have pledged to deploy 300 cease-fire monitors there by the end of the month, international envoy Kofi Annan said Tuesday. He warned, however, that the world can't wait forever for the truce to work.

Annan said in Geneva that there has been "a spate of bombings that are really worrying" and that the UN's cease-fire-monitoring mission "is the only remaining chance to stabilize the country."

"There is a profound concern that the country could otherwise descend into full civil war, and the implications of that are frightening," he said. "We cannot allow that to happen."

Annan spoke to reporters after briefing the UN Security Council by videoconference from Geneva, where he warned that failure to prevent a civil war "will not only affect Syria, it will have an impact on the whole region."

Annan said he also told the Security Council that "unacceptable levels of violence and abuse" are continuing in Syria -- that government troops are still present in and around cities and towns and human rights violations are extensive and may be increasing.

"There have been worrying episodes of violence by the government, but we have also seen attacks against government forces, troops and installations. And there have been a spate of bombings that are really worrying and I'm sure creates incredible insecurity among the civilian population," he said.

He said there has been "some decrease in the military activities, but there are still serious violations in the cessation of violence that was agreed and the level of violence and abuses are unacceptable," he said.

Annan warned that his six-point peace plan aimed at halting the fighting and initiating political talks to end the 14-month conflict is not an open-ended one. The Security Council has endorsed Annan's plan and authorized 300 unarmed military observers to monitor actions by Syrian President Bashar Assad's regime and opposition for three months.

The fighting between the two sides is estimated to have killed more than 9,000 people.

"We may well conclude down the line that it doesn't work and a different tack has to be taken, and that will be a very sad day, and a tough day for the region," he said.

Yet, he also tried to sound a note of optimism.

"We've been small in numbers, but even where we've been able to place two or three observers, they've had a calming effect," he said. "And I think that when they are fully deployed and working as a team, establishing relations with the people, we will see much greater impact on the work that they are there to do."