OSLO (Reuters) - Rich nations' emissions of gases blamed for global warming risk rebounding in coming years after falling overall since 1990 amid the collapse of Soviet-era industries, United Nations data showed on Thursday.

Compared to 1990, the greenhouse gas emissions of 40 developed nations including former Communist states were down 5.9 percent by 2003, slightly exceeding a goal of a cut of 5.2 percent by 2008-12 set by the U.N.'s Kyoto protocol.

"Further efforts are required to sustain these reductions and to cut the emissions further," the Bonn-based Secretariat of the U.N. Framework Convention on Climate Change (UNFCCC), of which Kyoto is a part, said in a report.

It projected that emissions could rise by 10.6 percent above 1990 levels by 2010, cautioning that most of the overall reductions dated from the early 1990s when smokestack industries in the former Soviet Union and eastern Europe shut down.

"Greenhouse gas projections indicate the possibility of emission growth by 2010. It means that ensuring sustained and deeper emission reductions remains a challenge for developed countries," said Richard Kinley, acting head of the Secretariat.

A U.N. meeting in Montreal, Canada, from Nov 28-Dec 9 will review Kyoto and ways to widen it to non-participants including the United States and developing nations like China and India when it runs out in 2012.

Many scientists say that a build-up of greenhouse gases -- from power plants, factories and cars -- are driving up temperatures and could cause catastrophic climate changes with more storms, floods, deserts and rising sea levels.

According to the UNFCCC data, Lithuania had made the deepest cuts at 66.2 percent below 1990 levels in 2003, followed by Baltic neighbours Latvia on 58.5 percent and Estonia on 50.8 percent.

Among other countries below 1990 levels, Russia's emissions were down 38.5 percent, Germany's down 18.2 percent, Britain's down 13.0 percent and France's down 1.9 percent.

At the other end of the scale, Spain was furthest above target with a 41.7 percent rise in emissions above 1990 in 2003, followed by Monaco at 37.8 percent, Portugal 36.7 percent, Greece 25.8 and Ireland 25.6 percent.

The United States, which pulled out of Kyoto in 2001 after President George W. Bush said it was too expensive and wrongly excluded poor nations from the first round of cuts, was 11th furthest above target at 13.3 percent above 1990 levels.