Chancellor Angela Merkel said she had agreed with the president-elect in a telephone conversation Thursday that their two nations must act in union to solve the world's problems. "Germany must, should and will take on responsibility," she said.

But in remarks to supporters a day later, the limits to German willingness were clear.

Germany has not forgotten an Obama speech in Berlin in June during which he called on the Germans to take on more of the fighting burden in Afghanistan, where German soldiers have rarely fought the Taliban.

Merkel told the youth section of her Christian Democratic Union (CDU) that Berlin would not accede to any request from the next US administration to send troops to southern Afghanistan, the scene of most fighting.

"Wherever Germany commits itself, a wholeness of military and civilian assistance should be visible," she said. She would be able to tell Obama that "just as well" as she had said it to President George W. Bush.

German forces, the third-biggest component in the International Security Assistance Force (ISAF), are based in safer northern Afghanistan. Other armies have borne the brunt of the fighting in the south.

Merkel may gain her chance to tell Obama fairly soon when she attends a G20 summit in Washington at the end of this week. World leaders hope to see Obama during their stay.

Enthusiasm for Obama has been huge in Berlin most of this year: that helped ensure a crowd of 200,000 heard his speech in a city park on July 24.

Former defense minister expects pressure from Obama

The Social Democrats (SPD), the other main party in the Merkel federal coalition, have claimed Obama's election as vindication for their own centre-left policies, but have also had an undertone of caution about Afghanistan.

Peter Struck, who heads the SPD parliamentary caucus and is a former German defense minister, told a Sunday newspaper, Bild am Sonntag, he expected Obama to seek more from NATO and its European members.

But if Obama requested German fighting troops in the south, "I would resist that most resolutely," he said. "There are limits."

He said Germany was already sending an extra 1,000 men to the north and offering advance-warning aircraft.

Foreign Minister Frank-Walter Steinmeier, the Social Democrat who is to challenge Merkel next year for the chancellorship, has already begun staking out that German position in diplomatic language.

He told a German newspaper, the Hamburger Abendblatt, on Saturday that Obama "highly appreciated" Germany's current contribution in Afghanistan. Obama would not just seek more troops but also more reconstruction aid.

"We are very close to Obama on this," he said.

Both Merkel and Steinmeier are driven on the troops issue by voter concerns about the Afghan war.

German leaders wary as elections loom on horizon

With an election coming up in September, neither camp wants a surge in German casualties, including those from suicide attackers, to trigger a new round of anguish over the deployment.

Surveys show most Germans think the country is doing enough in Afghanistan. A Forsa poll found 80 percent agree a US request for more troops should be refused and only 15 percent disagree.

However neither main party wants to upset Obama at this stage by criticizing him.

The Germans are eager to move forward with Washington on many issues "in a spirit of togetherness," Merkel said.

She told the Bild am Sonntag on Sunday those issues included "stabilizing Afghanistan," fixing the global financial crisis, fighting global warming and improving human rights.

Steinmeier has already begun plans to demonstrate goodwill on another front, setting up plans to pay a call on the US-backed government in Iraq next year and asking aides to draw up substantive aid plans for Iraq.

That in itself is remarkable, since Steinmeier, as chief of staff to former German chancellor Gerhard Schroeder, was a leading figure in Germany's refusal to assist the United States in the 2003 Gulf War.