FACTBOX: What is the Kyoto Protocol?

(Reuters) - Delegates from up to 190 nations will meet in Bangkok from March 31-April 4 to start work on a new U.N. pact to fight climate change and succeed the Kyoto Protocol.

Here are some frequently asked questions about Kyoto:

* WHAT IS THE KYOTO PROTOCOL?

-- It is a pact agreed by governments at a 1997 U.N. conference in Kyoto, Japan, to reduce greenhouse gases emitted by developed countries to at least 5 percent below 1990 levels by 2008-12. More than 170 nations have ratified the pact.

* IS IT THE FIRST AGREEMENT OF ITS KIND?

-- Governments agreed to tackle climate change at an "Earth Summit" in Rio de Janeiro in 1992 with non-binding targets. Kyoto is the follow-up.

* SO IT IS LEGALLY BINDING?

-- Kyoto has legal force from February 16, 2005. The United States, long the world's biggest source of emissions but which is being surpassed by China, came out against the pact in 2001. President George W. Bush reckoned it would be too expensive and wrongly omits 2012 emissions targets for developing nations.

* HOW WILL IT BE ENFORCED?