By Gerard Wynn

MONACO, Feb 21 (Reuters) - The United Nations Environment Programme (UNEP) launched a new online network on Thursday to help countries, cities and firms aiming to be "climate neutral" exchange ideas on ways to cut greenhouse gas emissions.

The Climate Neutral Network will connect people around the world who have committed to become climate neutral by reducing and offsetting their emissions of the gases blamed for heating the planet, said Achim Steiner, head of UNEP.

"The idea is to share ideas," he said.

UNEP, which is hosting 154-nation climate talks in Monaco, aims to be climate neutral itself in 2008, with the whole United Nations due to follow.

Monaco said on Thursday it would become the fifth country to commit to carbon neutrality under the UNEP project, joining Costa Rica, Iceland, Norway and New Zealand.

"We aim very quickly to come up with climate neutrality for the principality ... we are joining (the project) today," environment minister Robert Calcagno told reporters.

Monaco, which famously hosts the high-octane Formula 1 motor-racing series each May, is making efforts to cut emissions by subsidising solar power, among other projects.

Four cities in Sweden, Norway, China and Canada also joined the scheme on Thursday, and five companies.

Pressure from investors and the public has prompted many cities and companies to commit to cutting emissions, but some dismiss carbon neutrality as a publicity stunt or "greenwash".

Critics say carbon offsetting -- paying others to cut emissions on your behalf, for example by planting trees or building wind farms -- allow individuals, businesses and governments to avoid taking action themselves.

Norway's environment minister Erik Solheim said on Thursday that his country could not achieve its target of being climate neutral by 2030 without using offsetting.

"It's (offsetting) absolutely necessary," Solheim said.

The Monaco climate conference is the biggest since December, when nearly 200 countries agreed in Bali, Indonesia to launch two-year talks on a successor to the Kyoto Protocol after 2012.

UNEP's Steiner said the new online network, which can be found at www.unep.org/climateneutral, would help those talks.

"As climate negotiations take place it's no reason to sit back and wait," he said.

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