Developed countries "have themaximum responsibility" for the emission of greenhouse gases, German Environment Minister Juergen Trittin said here Thursday.

"The most powerful nations have to pay attention to the demandsof developing countries," Trittin said at the closing of the UN conference on climate change with participation of environment ministers from about 80 countries.

He said agreement will be reached on a second period of commitments by 2012, when the Kyoto Protocol expires.

The Kyoto deal aims to reduce the six major heat-trapping gasesincluding carbon dioxide by 5 percent, a first small step in the fight against global warming.

Under the protocol, industrialized countries together must reduce man-made emissions by 5 percent by 2012 versus 1990 levels.

Spain said it will have difficulties in meeting the targets forthe control of greenhouse gas emissions because it increased 40 percent of them since 1990.

Arturo Aizpiri, Spanish minister for Pollution and Climate Change Prevention, recognized that the excess in gas emission hasto be reduced through suitable mechanisms.

On its part, Argentina proposed to hold two informal meetings in 2005 to discuss new measures to control the global climate warming.

The United States, the biggest polluter in the world with 25 percent of heat-trapping greenhouse gas emissions, has refused to ratify the Kyoto protocol on cutting emissions of six key gases, which comes into effect in February.

US President George W. Bush rejected the protocol after he tookoffice in 2001 saying it would cost US industry too much to meet the gas emission cuts under the accord.