IMF chief Dominique Strauss-Kahn, jailed in New York for alleged rape assault.

IMF chief Dominique Strauss-Kahn

IMF chief Dominique Strauss-Kahn, jailed in New York for alleged rape assault, faced growing pressure Wednesday after a top US official cast doubt on his ability to lead the world lender.

"He's obviously not in the position to run the IMF," US Treasury Secretary Timothy Geithner said in his first public comments on the case, which could see Strauss-Kahn, once a favorite for France's presidency, spend years behind bars.

Strauss-Kahn, who spent his second night in New York City's notorious Rikers Island jail complex, faces a long prison sentence if convicted. He has denied all the charges against him.

IMF spokesman William Murray said the Washington-based organization has not been in touch with Strauss-Kahn since his arrest in the first-class section of an Air France jet Saturday afternoon.

IMF Spoksman - William Murray

"We are aware of widespread speculation about the managing director's status," he added.

British Foreign Secretary William Hague said Strauss-Kahn was in a "very difficult position," and that this must not interfere with the IMF's work, but said London did not have a view on whether he should remain in his post.

While Japan, the second largest donor to the IMF after the United States, said it was too early to discuss a replacement for Strauss-Kahn.

On Monday, a judge refused to grant bail to Strauss-Kahn, saying he posed a flight risk because he might try to escape to France. A new court hearing is due Friday.

A grand jury is due to convene to decide whether there is enough evidence in the accusations to proceed to trial. Such proceedings are secret, and the Manhattan District Attorney's office would not comment on progress.

Whatever happens this week, the bottom has fallen out of Strauss-Kahn's world.

He was widely seen as the man who could unseat President Nicolas Sarkozy in 2012 elections.

Now he occupies a single cell on Rikers Island, along with thousands of other detainees, most of them too poor to afford their bail.