Updated from 11:16 a.m.

Barrett Resources


said Monday its board of directors will meet within 10 days to consider a $55-a-share hostile tender offer from

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Shell Oil


"Until such time, the Company urges shareholders to take no action with respect to their holdings of Barrett," the company said in statement issued after the close of trading.

Shell, a subsidiary of

Royal Dutch/Shell Group

, said Monday's cash tender offer represents a 24% premium over Barrett's share price of $44.25 on Feb. 28, the last trading day before Shell's initial acquisition proposal.

Shares of Denver-based Barrett, a natural gas and crude oil exploration and production company, closed Monday at $62, off 52 cents for the day. Still, the closing price was well above Shell's offer, indicating an expectation among investors that a better deal could be in the offing.

On March 8, Barrett

rejected an unsolicited $1.8 billion bid from Royal Dutch/Shell Group and invited better offers. Royal Dutch said it expected a fight for control of Barrett, which has a "poison pill" defense that wards off hostile bids by triggering a massive issue of shares.

"We consider it a positive sign that Peter Dea and Barrett's Board of Directors have said they are considering strategic alternatives, but it is not clear that they are committed to the sale of the company," Shell said. "That is why Shell has chosen to take its offer directly to the Barrett shareholders rather than participate in the auction process proposed by Barrett's Board."

Shell's offer is contingent on the acquisition of at least a majority of the outstanding shares and will expire on April 6.