Berlin -- German Chancellor Angela Merkel will address a joint session of the US Congress and meet President Barack Obama on Tuesday ahead of the 20th anniversary of the fall of the Berlin Wall.

In her first US visit since her re-election in September to a second term, Merkel will speak on the demise of European communism and the future of transatlantic ties, in the run-up to the Berlin festivities on November 9.

Beyond the pomp, the trip will focus on a range of strategic issues including Afghanistan, Iran, standards for financial market regulation and climate change, Merkel's spokesman Ulrich Wilhelm said.

In her weekly podcast, Merkel called the invitation a "great honour" and said she would use the occasion to thank the United States for backing German unification in 1990 -- 11 months after the Wall's fall -- with "great enthusiasm and fondness".

Merkel, who grew up in communist East Germany, will be only the second German chancellor to address the US legislature, after Konrad Adenauer spoke to separate sessions of each chamber in 1957.

The invitation, extended by House Speaker Nancy Pelosi, has largely silenced early media reports of chilly relations between Merkel and Obama.

But Josef Braml of the German Council on Foreign Relations in Berlin said Merkel would be naive to think the honour did not come at a price.

"It is a gesture where a service is expected in return: the German government should do more to help shoulder the burden of international commitments," notably in Afghanistan as Obama reassesses the US deployment.

With around 4,200 soldiers, Germany is currently the number-three supplier of foreign troops in the war-ravaged country after the United States and Canada.

Braml said now that the German election is over, Merkel was likely to face requests for more forces and training personnel for Afghanistan, more money to stabilise neighbouring Pakistan, as well as firm backing for UN sanctions against Iran if it continues to pursue sensitive nuclear work.

Germany is one of Iran's top trading partners and one of six world powers working to settle the dispute with Tehran.

"The grace period is over -- now we need to deliver," Braml said, warning that a refusal risked greatly diminishing Berlin's influence in Washington.

Merkel, who leaned hard on Obama's predecessor George W. Bush to make concessions on climate change, also aims to make headway ahead of the UN conference in Copenhagen in December, where 192 countries will work toward an accord on reducing greenhouse gas emissions.

"It is not yet clear whether Copenhagen will be a success but the European Union and Germany in particular will push for us to achieve ambitious, forward-looking political resolutions," she said.

Obama's talks with Merkel come ahead of a EU-US summit Tuesday.

The chancellor is also seeking proof that the United States is serious about new market rules to head off future global financial crises.

"The international financial and economic crisis has not yet been surmounted and we have not yet ensured that such a crisis cannot repeat itself," she said.

"There is a lot of concern in Berlin that Washington will not be as rigorous in its pursuit of reforms and will return to old ways of oversight," said Jackson Janes, head of the American Institute for Contemporary German Studies in Washington.

Merkel's new foreign minister, Guido Westerwelle, is to follow on her heels with a trip to Washington Thursday, sources said, including talks with US Secretary of State Hillary Clinton.

Westerwelle, head of the pro-business Free Democrats, junior partners in the new centre-right government, managed to insert a passage into the coalition agreement calling for the estimated 10 to 20 US nuclear warheads on German soil to be removed.

The request is expected to fall on deaf ears in Washington, and observers are eager to see whether Merkel will take up the charge or leave it to Westerwelle.

AFP/Expatica