The immediate future of Yahoo!, the world's leading Internet portal, was in doubt yesterday after its shares were halted pending an announcement.

Nasdaq ordered that trading be suspended after the company's chief financial officer, Ms Susan Decker, pulled out of a Merrill Lynch Internet conference scheduled for today. The company is understood to have been preparing an announcement after the end of trading.

Mr Henry Blodget, Merrill Lynch's Internet analyst, said it was the first time Yahoo! had pulled out of a conference at such short notice. He speculated the company might be about to announce a profits warning, a restructuring, a significant acquisition or a senior management change.

The most mundane reason would be a profits warning as the company suffers from the slowdown in online advertising that represents 90 per cent of its revenues. Mr Blodget previously indicated Yahoo! advertising revenues could fall as much as 25 per cent during the current quarter.

Before they were halted, Yahoo! shares had fallen yesterday by 6.5 per cent to $20.96 (€22.58), the lowest since September 1998, and almost 90 per cent below the peak of $205 last year.