Cisco Systems Inc needs more help from shareholders to meet the acceptance threshold in its bid to buy Norway's Tandberg ASA and create the global leader in videoconferencing equipment.

The world's biggest network equipment maker on Wednesday ruled out any further extension in its $3.4 billion offer whose expiry has been put back again to 1630 GMT on Thursday Dec. 3.

Analysts say that Cisco will gain operational control of Tandberg at the current 84 percent of acceptances for its 170 crown-per-share bid, limiting the influence of minority owners.

If Cisco meets its 90 percent threshold, it can automatically buy them out.

Cisco said it would announce whether it had gained the desired acceptances shortly after the bid ends.

If not, Cisco will determine whether to withdraw the offer or waive this (90 percent) condition, it said.

Shares in Tandberg were up nearly 2 percent at 164.60 crowns by 1107 GMT, below the bid price due to the delay shareholders face in receiving cash from Cisco.

Cisco has extended the offer three times and last month raised it by 10 percent to win over sceptical shareholders.

The original offer was rejected by more than 90 percent of Tandberg shareholders. That triggered some concerns that Cisco might walk away, but most analysts said the deal was too crucial for it to drop.

Cisco Chief Executive John Chambers has said online videoconferencing was a key growth area that is on the brink of more widespread adoption.

High-quality, real-time videoconferencing can help companies cut travel costs, and Cisco believes it can do more, such as helping businesses like retailers, banks and hospitals launch services from remote locations.

Tandberg is the leading videoconferencing equipment maker, and the company's products fill a crucial gap between Cisco's high-end TelePresence conferencing products and WebEx desktop video service.

Tandberg holds 40 percent of the mid-tier market for videoconferencing, according to Wainhouse Research.

(Reporting by Oslo newsroom; editing by David Cowell)