LONDON (AP) -- The international economy is still fragile and vulnerable to shocks despite recent improvements in financial markets, the managing director of the International Monetary Fund said Monday.

Dominique Strauss-Kahn told business leaders in London that he believes the worst of the economic crisis has passed -- but that problems remained.

"The economy remains very much in holding pattern -- stable and getting better but still highly vulnerable," he said in a speech to the Confederation of British Industry, the country's main business lobby group.

"It is difficult to claim that the crisis is over when unemployment is at historic highs and getting higher still."

Strauss-Kahn also said Asian countries needed to help drive international growth. American households have traditionally been the main drivers of international growth, consuming goods exported by other countries, but Strauss-Kahn said this model needs to change.

"If we are to have sustained global growth, somebody else needs to step in," he said. "China and other emerging Asian economies are shifting from exports to domestic demand but they have some way to go."

British Prime Minister Gordon Brown, also speaking at the same conference, agreed investment from China could help drive Britain's economic recovery.

"In our new growth strategy I want not just hundreds but thousands of Chinese companies in Britain, and British companies in China," Brown said.

Britain is struggling with a major downturn despite attempts by the government and Bank of England to boost the economy, including holding interest rates at a record low of 0.5 percent since March, an unprecedented 175 billion pound ($290 billion) injection into the money supply and billions more through fiscal measures.

Brown said in the speech that he does not expect to withdraw fiscal support soon.

"Choking off recovery by turning off the life support for our economies prematurely would be fatal to British jobs, British growth and British prosperity for years," he said.

Brown also said he wants to improve rail links between Britain and continental Europe.

He said he wants to build a high-speed line that would link the north of Britain to European cities like Cologne and Amsterdam. At the moment, the rail links between Britain and the rest of Europe originate in London.