Berlin  - US President Barack Obama and German Chancellor Angela Merkel have moved to lay aside differences ahead of next week's summit of the world's big economies by agreeing that market reform will be the key issue on the meeting's agenda, a spokesman in Berlin said Friday.

The buildup to the Group of 20 summit of the world's most advanced powers and leading emerging economies in London has been accompanied by tensions between Washington and Europe over the need to help spur global economic growth with more government spending.

While Obama has called for bold action to underpin a recovery in the world economy, the Europeans, led by Merkel, have resisted a push for more government spending and instead stressed the importance of bolstering international financial market regulation.

But speaking in Berlin, Merkel spokesman Ulrich Wilhelm said that the US and German leaders had agreed during a conference call Thursday that overhauling the world's financial markets would play a central role at the London meeting.

Thursday's 40-minute talk between Obama and Merkel also came in the run-up to next week's 60th anniversary NATO summit, which is to be jointly hosted by France and Germany.

Merkel and Obama are also scheduled to meet in the German town of Baden-Baden on April 3 on the sidelines of the NATO summit.

In addition, the discussion between the US and German leaders came as Washington moved to again boost its military commitment to Afghanistan in a bid to defeat militants in both Afghanistan and neighbouring Pakistan.

But Wilhelm said that Obama had not called on Germany to bolster its troop commitments to Afghanistan.

During their talks, Obama and Merkel also discussed the fate of the troubled carmaker Opel, which is the German offshoot of the embattled US giant auto group General Motors Corp, which is due to present a restructuring plan in the coming days.

Merkel's government has been resisting mounting a bailout for Opel as it considers what action to take to overcome the plight of the GM German group, which has also been badly hit by the global car crisis.

Opel has already proposed forming a new European auto group, taking in GM's other European operations - Vauxhall and Saab. (dpa)