Critics of Steve Ballmer, Microsoft's chief executive, accuse him of many things, but indecisiveness is seldom one of them.

Yet the silence that has descended over the software group's bid for Yahoo this week has left a perception that Microsoft has put itself into a tactical bind.

The questions have been growing since Mr Ballmer let an ultimatum expire last Saturday without taking the next threatened step, of launching an all-out hostile takeover battle.

Since then, silence has come to seem like hesitation, which in turn has fed an impression of indecision.

Other takeover experts say that to threaten a hostile bid without following through demonstrates tactical weakness.

"They crossed that Rubicon when they launched their offer, and again when they issued the ultimatum," said one Silicon Valley investment banker. The failure to act looks like a lack of resolve, this person added.

Others suggest that it is another sign of Microsoft's inexperience in the takeover game. While most CEOs in this position are prepared to follow a closely-choreographed script laid out by the investment bankers, Mr Ballmer has insisted on calling the shots himself and resisted making the conventional plays, according to a person familiar with the company's deliberations.

One sign of that was Mr Ballmer's warning, made in the ultimatum issued in early April, that he would cut the value of Microsoft's offer unless Yahoo agreed to negotiations. That unusual threat was a mis-step that antagonised Yahoo shareholders, says one takeover expert.

Adding to the sense of tactical uncertainty this week is an apparent willingness on Microsoft's part to contemplate abandoning its offer altogether in the face of Yahoo's intransigence.

"They lose a lot of credibility if they turn around and walk away now," said the investment banker.

This, of course, could we ll be all part of a delicate negotiating position. As long as Yahoo knew Microsoft was bent on following through with a deal, it could hold out for a higher price than the $31 a share originally offered, said one person close to the situation.

"With Ballmer willing to walk, that stranglehold is broken and it may be possible to bridge the gap [on price]," this person said.

If so, then the important question is not whether the Microsoft CEO is dithering over whether to abandon his bid but whether Yahoo's board believes he is. Projecting a sense of indecision may, if anything, help the Microsoft case.

All of this leaves open the real question that Microsoft faces: how to bring Yahoo to the negotiating table and complete a deal without being forced to pay significantly more than it has already offered.

"I presume they had a plan B [in case the ultimatum failed to force Yahoo into submission]," said Morton Pierce, a mergers and acquisition lawyer at Dewey & LeBoeuf. In spite of the unusual hesitation, that plan is likely to become apparent soon, he added.