* Rebels seized power from president earlier this year
* U.N. officials suggest larger peacekeeping force needed (Adds Security Council statement, bullets, byline)
By Michelle Nichols
UNITED NATIONS, Aug 14 (Reuters) - The Central African Republic is on the brink of collapse and the crisis is threatening to spread beyond its borders, senior U.N. officials said on Wednesday as they urged the Security Council to help fund and support an African Union peacekeeping force.
The landlocked former French colony - one of the poorest places on earth - has been plunged into chaos since the Seleka rebels seized power from President Francois Bozize four months ago, triggering a humanitarian crisis in the heart of Africa.
The African Union this month rolled an existing 1,100-strong regional peacekeeping mission, known as MICOPAX, into a new, larger AU peacekeeping force. The number of troops will be more than tripled to 3,600 and the force has an AU mandate to protect civilians, help stabilize the country and restore government.
"The African Union has requested financial, logistical and technical support. We have recommended to the council to provide this support. We have also recommended to better adapt the U.N. (political) mission to the current situation," U.N. envoy to the Central African Republic, retired Lieutenant General Babacar Gaye, said.
The African Union and United Nations plan to send experts to the Central African Republic shortly to assess exactly what was needed and U.N. diplomats said that on the basis of those reports the Security Council would respond with a resolution.
Gaye and U.N. Assistant Secretary-General for Human Rights Ivan Simonovic both signaled to the Security Council that the AU force would not be enough to combat the crisis in the Central African Republic, which borders six other states.
"A much larger and nationally more diversified force is needed to provide security and protect the population," Simonovic said. "Such a force would also prevent foreign rebel groups, such as the Lord's Resistance Army or Islamist extremist groups, from finding a safe haven in the country."
The U.N. Security Council said in a statement after Wednesday's meeting that it was willing "to consider all potential options to stabilize the Central African Republic (CAR)."
"The members of the Security Council expressed deep concern at the security situation in CAR, characterized by a total breakdown in law and order, and the absence of the rule of law," the statement said.
"They stressed that the armed conflict and crisis in CAR pose a serious threat to the stability of the CAR and the region," it said.
U.N. aid chief Valerie Amos told the council the Central African Republic was at risk of becoming a failed state.
She said every one of the country's 4.6 million people - half of whom are children - had been affected by the crisis. About 1.6 million of them are in dire need of assistance. More than 206,000 people have been internally displaced and nearly 60,000 have fled to neighboring countries.
"It is critical for the continued safety of humanitarian operations that the AU mission has the funds and logistical support to operate effectively," Amos told the 15-member Security Council.
"The failure to act now could not only prolong and exacerbate the appalling conditions the people of the Central African Republic have had to endure, but could also see the crisis spread beyond its borders and throughout a region already facing enormous challenges," she said. (Reporting by Michelle Nichols; Editing by Cynthia Osterman and Eric Beech)