Germany expects difficult negotiations with the United States on climate protection at the June summit of the Group of Eight (G8) industrial nations, a German official said on Tuesday.

Preparatory talks ahead of the summit had not produced satisfactory progress, said Bernd Pfaffenbach, who is German chancellor Angela Merkel's envoy to the G8.

He reiterated that Merkel still had the ambition to move ahead on climate protection and wanted the G8 summit, which will be held on June 6-8 under the German presidency, to at least send a signal of joint efforts on climate change.

Germany has made climate change a key theme of this year's G8 summit and expects G8 leaders to held serious discussions on a new international regime to succeed the Kyoto Protocol to reduce greenhouse gas emissions.

Pfaffenbach indicated Berlin's disappointment that the United States was not yet ready to go along with any new international climate protection regime.

The 1997 Kyoto Protocol, which expires at the end of 2012, has been almost crippled after it was abandoned by the United States in March 2001.

Germany helped broker an agreement last month under which the 27 EU member states will reduce greenhouse gas emissions by 20 percent from 1990 levels over the next 13 years.