Berlin - German Chancellor Angela Merkel departed on a trip to the US on Monday, where she was due to address a joint session of the US Congress, an historic opportunity granted to few foreign leaders. The rare invitation, extended to around 100 world leaders in American history, was meant to mark the end of the Cold War when the Berlin Wall toppled on November 9, 1989.

However, Merkel has indicated she will also tell Congress it is time for the US to take on a more active role in reducing the greenhouse gases blamed for climate change.

The EU wants wealthy economies to commit to reaching ambitious new emission reduction goals by 2020, to be hammered out during a UN summit in Copenhagen in December.

During her two-day visit, less than a week after being sworn into her second term in office, Merkel is also to discuss with US President Barack Obama topics including developments in Afghanistan.

The leaders were to address "the question of the further strategy for Afghanistan," a German government spokesman said shortly before Merkel's departure.

Other issues were Iran's response to an international proposal aimed at limiting the country's nuclear enrichment programme, and the status of the Middle East peace process.

The leaders were also expected to discuss the global economic situation, spokesman Ulrich Wilhelm said.

Speaking to journalists in Berlin, Wilhelm declined to comment on the likely impact of Merkel's speech to Congress, in which she is due to thank the US for its role in helping Germany to reunite peacefully at the end of the Cold War.

Asked whether her speech would have an historic impact, Wilhelm commented that the distinction "only ever materializes in retrospect." (dpa)