U.S. chemicals group DuPont extended its $6 billion takeover bid for Danisco by four weeks after holders of only 6 percent of the Danish company's shares had accepted the offer.

The group's estimate for acceptances up to March 29 was far below the 90 percent acceptance level that DuPont has required to carry out the deal and delist Danisco.

The extension of the 665 Danish crowns ($125.6) per share offer for the Danish food ingredients and enzymes producer came amid growing doubts about whether DuPont will be able to carry out the deal following recent turbulence in the markets.

Analysts said this week that market turmoil in the wake of crises in the Middle East and Japan would make DuPont increasingly disinclined to raise its bid, while at the same time Danisco many shareholders were holding out for more money.

Acceptances of the bid crept up by only one percentage point from the 5 percent acceptance level that DuPont announced the previous time it extended the bid on February 18.

DuPont said in the statement that the acceptance level was in line with similar past voluntary tender offers in Denmark at this stage of the Offer.

But Alm. Brand analyst Michael Friis Jorgensen said: The acceptance level of 6 percent is only marginally higher than the last time ... and I think it suggests that it will be difficult for them.

I think it indicates that it will be very difficult for them at the current price to get acceptance of the offer, Jorgensen said.

Shares in Danisco, which have hovered just below the bid level since the deal was announced in January, were down 0.08 percent at 663.50 crowns at 0858 GMT (4:58 a.m. ET), underperforming a 0.87 percent rise in the Copenhagen bourse bluechip index <.OMXC20>.

DuPont has repeatedly said it will not raise its bid, which was announced in January and recommended by Danisco's board.

The U.S. company said it was awaiting regulatory approval for the deal in China and the European Union, but continues to expect that those approvals would be obtained.

DuPont has already received competition approvals in the United States.

The offer period would run until April 29 instead of April 1, and the result of the offer is expected to be published on May 2, DuPont said in a statement.

The terms and conditions of the offer as set forth in the offer document remained unchanged, DuPont added.

($1=5.294 Danish Crown)

(Reporting by Mette Fraende, Teis Jensen and John Acher; Editing by Jon Loades-Carter and Hans Peters)