* Brahimi says situation in Syria "bad and getting worse"
* Reform not enough, change is needed now, Brahimi said
* First U.N. Security Council briefing by Brahimi
By Michelle Nichols
UNITED NATIONS, Sept 24 (Reuters) - The international mediator on Syria said on Monday he has "a few ideas" but not a full plan on how to end the country's 18-month conflict, which he described as "extremely bad and getting worse."
Lakhdar Brahimi offered that assessment after his first briefing to the U.N. Security Council since replacing Kofi Annan as the U.N.-Arab League mediator on Sept. 1. In his first month on the job, Brahimi met with Syrian Pr e sident Bashar al-Assad in Damascus and visited refugee camps in Turkey and Jordan.
"I do not have a full plan for the moment, but I have a few ideas," the veteran Algerian diplomat said. "I have agreed with the council I will come back here as soon as possible with more ideas on how we move forward."
"The situation in Syria is extremely bad and getting worse. It is a threat to the region and a threat to peace and security in the world," he told reporters. "There is a stalemate ... but I think we will find an opening in the not too distant future."
Brahimi declined to elaborate.
The United Nations says nearly 20,000 people have been killed in the conflict. More than 250,000 Syrians have fled to neighboring Turkey, Jordan, Lebanon and Iraq, with more than 100,000 of those leaving in August alone.
Council diplomats, speaking on the condition of anonymity, described Brahimi's assessment of the conflict as downbeat, saying that despite government claims it was committed to reform, Damascus was instead seeking to portray the uprising as a foreign conspiracy and return to how things used to be.
"You cannot go back to the Syria of the past," Brahimi said. "Reform is not enough anymore, what is needed is change."
One diplomat said that while Brahimi did not reveal much to the council about his plans, he was "solid" in laying the bulk of the blame for the conflict with Assad's government.
While decrying the violence, diplomats offered no new ideas for how to solve it.
"The situation in Syria is grave. We need to do everything we can to end the violence and the killing of so many innocent people," German Foreign Minister Guido Westerwelle told reporters. Germany is president of the council for September.
As Syria spirals deeper into civil war, the Security Council has been paralyzed as Russia and China have blocked three Western-backed resolutions that criticized Assad and threatened sanctions.
Annan blamed the Security Council impasse for hampering his six-month bid to broker peace and leading to his decision to step down. Diplomats have tried to play down expectations for Brahimi's mission and the former Algerian foreign minister has described the task of brokering peace as "nearly impossible."
In a statement on Monday, the 15-member Security Council expressed grave concern about the situation in Syria and offered its full and strong support to Brahimi.
Diplomats said Brahimi made a plea to the Security Council for strong unified support, saying there could be no progress without it: "You all say you support me individually, why don't you support me collectively? It shouldn't be very difficult."
Westerwelle said former U.N. Secretary-General Annan's six-point plan for peace in Syria was still relevant.
The plan, which failed to take hold, calls for an end to violence, a Syrian-led political process, access for aid, the release of arbitrarily detained people, freedom of movement for journalists and the freedom to protest peacefully.
Brahimi said it was one of the "elements in my toolbox."