UPDATE 1-Swiss Re estimates Sandy claims burden at $900 mln

* Swiss Re says overall market losses estimated at $20-25 bln

* Claims estimate uncertain due to ongoing assessment process

* Shares indicated to fall 0.8 percent

ZURICH, Nov 26 (Reuters) - Swiss Re said on Monday it estimated its claims burden from hurricane Sandy, which hit the United States last month, at $900 million.

The superstorm, which killed 132 people in the United States and Canada on Oct. 29, led to power outages, disruptions of public transport and damage to other infrastructure that have made recovery efforts difficult and complicate the loss assessment process, the reinsurer said in a statement.

"Our claims estimate therefore is subject to a higher than usual degree of uncertainty and may need to be subsequently adjusted," Swiss Re said.

It said overall market losses were estimated at $20-25 billion.

German rival Munich Re said it expected a hit in the mid hundreds of millions of euros from Sandy.

Shares in Swiss Re were indicated to open 0.8 percent lower following the news, according to premarket indications from bank Julius Baer.