New York: Yahoo president Susan Decker has defended the company's web search advertising deal with larger rival Google, saying some investors and industry participants had yet to understand its advantages.

But she would not discuss reports of an executive exodus and an impending reorganisation of the company's products division that sent Yahoo shares down more than three per cent on Friday.

Decker focused comments on concerns that the Google deal eventually would cut into Yahoo's competitive position against Google, which has steadily grown an already-dominant share in the search market.

Yahoo still aims to build up its position in search and views it as inseparable from bolstering growth in other online ad markets, such as graphical display. Tests the two companies had conducted also showed the deal would not prevent Yahoo's Panama search advertising system from gaining ground. The deal would help Yahoo make money off of less-used search terms, for one, she said.

"It is really a back-fill in places where we're not doing much business," Decker said. "It's our choice every day whether and how we might serve ads from Yahoo or Google, or a third party if we opened it up further."

Shares in Yahoo are down 16 per cent since the company ended buyout talks with Microsoft Corp last week and instead forged a non-exclusive ad deal with Google for up to 10 years.

Investor concerns over Yahoo's future have also mounted amid daily reports of executives leaving, including Jeff Weiner, executive vice-president of its network division, and Qi Lu, the top engineer for Panama.

Some of those departures may stem from efforts to reorganise Yahoo's products group - including e-mail and search - and integrate their operations on a global level.