Josef Ackermann, chief executive of Deutsche Bank, has turned down an approach from Citigroup to take charge of the US bank, underlining the lack of high-profile external candidates for the job.

Mr Ackermann was asked if he would be interested in becoming Citigroup's chairman and chief executive following the resignation of Chuck Prince. He "was approached, but said he was not available," according to an informed source.

Many Citi executives and shareholders have been urging the board to find an external heavy hitter who could help restore confidence in the troubled company. But there has been a lack of interest among senior industry executives, many of whom believe the company faces serious problems.

The leading internal candidate is Vikram Pandit, the former Morgan Stanley executive who is head of Citi's institutional businesses, according to someone close to the process. Mr Pandit is highly regarded by Robert Rubin, the former US treasury secretary who became chairman when Mr Prince resigned a month ago.

One option would be for Mr Rubin to stay on as chairman with Mr Pandit as chief executive. Other names discussed by the Citi search committee include Dick Kovacevich, chairman of Wells Fargo, and Sir Fred Goodwin, chief executive of Royal Bank of Scotland. But neither would be interested, according to people familiar with their thinking.

US treasury secretary Hank Paulson this week quashed speculation that he might be persuaded to take on the Citi job. He said he was staying in his post for the rest of the Bush presidency.

The Citi committee has discussed a number of former Citi executives but the only serious contender has been Bob Willumstad, who quit as chief operating officer in 2005.

There has been industry speculation about Jay Fishman, the former Citi executive who now heads Travelers, the US insurer. But Mr Fishman has made clear he would not be interested.

Mr Ackermann (59), said on November 13th he was "happy staying in Germany" and that he had not been asked about the jobs at Citigroup or Merrill Lynch. Shortly afterwards Citigroup approached Mr Ackermann, said a person close to the Deutsche Bank boss.