NEW YORK, FEB. 9 -- American Standard Inc. urged its stockholders today to reject Black & Decker Corp.'s sweetened $2.1 billion buyout offer and said it had adopted a "poison pill" defense aimed at thwarting hostile takeovers.

The building products concern also said it was considering several alternatives to Black & Decker's $65-a-share bid, including a restructuring, leveraged buyout or a friendly merger with another company.

American Standard said its financial adviser had been approached by several companies interested in possibly making a bid, but it refused to identify them.

American Standard stock rose 12 1/2 cents a share to $67 on the New York Stock Exchange. Black & Decker was up 25 cents at $19.37 1/2.

Black & Decker, a Towson, Md., tool and appliance maker, raised its offer last week from $56 for each of American Standard's 31.2 million common shares outstanding and then indicated Monday that it might be willing to go even higher than $65.

Barbara Lucas, a spokeswoman for Black & Decker, said the company was reviewing American Standard's latest response and had no further comment.

Analysts speculated the bidding would not go much higher, based on American Standard's underlying value. "You're getting to the point where you're into a reasonable value range," said Katherine M. Stults, an analyst with the investment firm Dean Witter Reynolds Inc.

"It was easy to say at $56 it was too cheap. When you're talking $67 or $68, it may not be easy to find a better offer," Stults said.

Others said Black & Decker's sweetened offer was generous given the current pessimistic climate for the construction industry. American Standard's products include plumbing and homebuilding supplies, automotive parts and security equipment.

"It's not a company with problems, but it would be a tough job showing much of an improvement in earnings because construction has slowed down," said Cornelius V. Sewell, an analyst with Argus Research Corp.

In a letter sent today, American Standard Chairman William B. Boyd told shareholders the board had turned down Black & Decker's bid and urged them to do the same.

American Standard also said today that it asked the U.S. District Court in Delaware to validate its antitakeover plan, which would allow its shareholders to buy American Standard stock from the company at $32.50 a share -- or half the price of Black & Decker's latest offer -- if a bidder acquired 15 percent or more of its stock.

Such a provision, called a "poison pill," is intended to make a hostile takeover prohibitively expensive.

Black & Decker had said its offer was conditioned on an agreement by American Standard shareholders that the company not be governed by a new antitakeover law in Delaware, where American Standard is incorporated.

The Delaware legislature tightened the state's takeover laws last month by requiring a bidder that acquires 15 percent of a company's stock to wait three years to complete a takeover.

The restriction does not apply if the bidder acquires at least 85 percent of the target company's stock in the same transaction that its holdings pass the 15 percent threshold.

Black & Decker and others have filed suit in federal court to challenge the new law.