UN force in Chad, CAR deploying too slowly - envoy

* Security situation in eastern Chad is poor - UN

* UN force small in Chad-Central African Republic

* Sudan-Chad tensions remain high, peace talks urged

UNITED NATIONS, July 28 (Reuters) - The slow deployment of U.N. peacekeepers in Chad and the Central African Republic has limited their ability to deal with the poor security situation in both countries, a U.N. official said on Tuesday.

U.N. special envoy to the countries, Victor Angelo, told the 15-nation Security Council the situation in northeastern Central African Republic "has been extremely insecure over the last three months and continues to be of serious concern as armed groups and bandits continue to operate in the area."

The Central African Republic is one of Africa's most isolated countries, where a weak government is struggling to end several internal rebellions and is battling the spillover of instability from neighboring Sudan and Chad.

In May, Chadian rebels launched an attack from Sudan against Chadian government forces in the east. The army repelled the rebels, but Angelo said the clashes further strained Chad's tense relations with neighboring Sudan and led to a "significant rise in crime, banditry and insecurity" across eastern Chad.

That has forced humanitarian aid agencies to curtail operations, he said, though the U.N. peacekeeping force in Chad and the Central African Republic, known as MINURCAT, has tried to provide escorts to humanitarian workers.

"The slow deployment of the force has limited the ability of MINURCAT to effectively ... provide the required safe and secure environment for humanitarian (workers), refugees ... and vulnerable populations," he said.

The peacekeeping force has a mandated full strength of around 5,500 soldiers and police, but Angelo told the council that only 46 percent of the force has been deployed. He said later that was because some countries that offered troops did not yet have the proper equipment for their soldiers.

He predicted the force would be near full deployment by the end of the year.

U.S. Deputy Ambassador Jeffrey DeLaurentis told the council Washington that 46 percent deployment was insufficient.

DeLaurentis expressed deep concern about the growing violence in the Central African Republic and said armed groups in Sudan and Chad jeopardized stability across the region.

"We urge both Chad and Sudan to work toward easing tensions and cooperating in implementing ... agreements aimed at normalizing relations between the two countries," he said.

British envoy David Quarrey also urged Chad and Sudan to resume peace talks. (Editing by Doina Chiacu)