that may foreshadow an attempt to block Republic Industries Inc.'s planned acquisition of ADT, North America's largest electronic security company.

Western, a Topeka, Kansas, energy company, increased its stake to 24.0 percent from 23.1 percent, according to a filing with the Securities and Exchange Commission.

Western said soon after Republic's offer for ADT last month that it might oppose the transaction, leading to speculation that Western also covets ADT.

"From our standpoint, (ADT) provides a natural growth strategy,'' George Norton, a Western Resources spokesman, said yesterday.

He declined to elaborate beyond the company's SEC filing, which said the company is "still considering its options'' on the Republic and ADT agreement.

Western's security unit, Westar Security, acquired closely held Sentry Protective Alarms in July, in Western's latest move to build its presence in the fast-growing security industry.

A spokesman for Republic, which is controlled by billionaire H. Wayne Huizenga, declined to comment. ADT couldn't be reached for comment. Republic, which has interests in trash hauling, electronic security and used-car superstores, plans to buy ADT for $3.98 billion in stock and assumed debt.

The combined companies would have 1.6 million security customers and estimated sales next year of $5 billion.

Western said in the SEC filing that it purchased 1.3 million ADT common shares at $16.00 to $19.75 each between July 16 and July 17, bringing its holdings to 32.1 million common shares through a unit called Westar Capital Inc. Western said in the filing it may sell its Republic shares if the Republic acquisition of ADT proceeds.

Western also is attempting a hostile takeover of Kansas City Power & Light Co., which threatens to derail that utility's planned acquisition of UtiliCorp United Inc. for $1.7 billion. -- Bloomberg