Memo to Europe: Be careful what you wish for.

Barack Obama, celebrated as the "anti-Bush" when he toured the continent last year as the Democratic presidential candidate, is headed back next week as US president to attend summits in London, Prague and on the French-German border.

After ordering the closing of the Guantanamo military prison, pledging to do more to combat global warming and renouncing his predecessor's "cowboy diplomacy," he will be looking for something in return - and analysts say he can't afford to leave empty-handed.