The European Union has urged China and the US to find a quick solution to the spy-plane stand-off, warning delay will only deepen the crisis.
Swedish prime minister, Goeran Persson, who currently holds the EU presidency, has voiced his concern at a "worrisome" escalation.
He said there was a need to slow things down.
"If things reach a stalemate on this problem, then things will get worse," he told a press conference.
The plane and its 24 crew members have been kept on China's Hainan Island since Sunday when it made an emergency landing after colliding with a Chinese fighter plane.
"I hope things will work out on the basis of case a law and general practice and that China will observe the international rules of the game," Mr Persson said.
He said increased trade between China and the US in recent years should show both sides the benefits of maintaining warm relations.