The head of the International Monetary Fund, Dominique Strauss-Kahn, has been charged by New York police over an alleged sex attack on a hotel maid.
Mr Strauss-Kahn, 62, was taken off an Air France plane at JFK airport just minutes before it left for Paris.
Police say the maid has now formally identified him in a line-up. He faces three charges which he denies.
The married former French finance minister is also considered a possible Socialist candidate for the presidency.
The BBC's Hugh Schofield, in Paris, says Mr Strauss-Kahn has been riding high in the polls and was seen as having a genuine chance of beating President Nicolas Sarkozy.
Martine Aubry, leader of France's Socialist Party, described news of his arrest as a "thunderbolt" which left her "astounded".
Mr Strauss-Kahn is expected to appear before a New York state court before 0100 local time on Monday (0500 GMT), despite reports of a delay as police apply for search warrants for further DNA evidence.
His lawyer, William Taylor, told Agence France-Presse news agency: "We saw him, he's doing OK. And we'll be in court with him later in the afternoon."
- Isn't it ironic how fast someone who is powerful can get into court quickly, but when you are the general public, you could sit in jail for days, weeks, months and in some cases years before getting your day in court.
Mr Strauss-Kahn had been scheduled to meet German Chancellor Angela Merkel on Sunday, but that meeting has now been cancelled, reports say.
On Monday he had planned to attend a meeting of European Union finance ministers in Brussels on Monday to discuss the bailouts of Portugal and Greece.
Correspondents say his detention is likely to complicate ongoing efforts to stabilise the finances of struggling eurozone member states.
The Euro fell half a cent to $1.4063 when Asian markets opened on Monday - a six-week low against the dollar - reflecting concerns about the impact the arrest could have on the bailout talks.
In a brief statement posted online on Sunday, an IMF spokeswoman acknowledged Mr Strauss-Kahn's arrest and said the organisation would not comment on the case.
"The IMF remains fully functioning and operational," she added.