WASHINGTON — Federal regulators appear to be resisting a formal probe of alleged anti-competitive practices of semiconductor giant Intel Corp., despite requests from members of Congress and corporate rivals.

For years, chipmaker Advanced Micro Devices Inc. has charged that Intel, the world's largest semiconductor-maker, violates U.S. antitrust laws. One accusation is that Intel gives rebates to computer-maker customers on the condition they not buy some AMD products, a charge the company included in a 2005 lawsuit against Intel.

The company, which is based in Santa Clara, Calif., "has illegally abused its monopoly position," AMD spokesman Mike Silverman said. "We encourage all antitrust enforcers around the world, including in the United States, to stop illegal conduct."

Chuck Mulloy, a spokesman for Intel, said the company's discounts are legal and benefit consumers. Intel denied offering rebates to customers that exclude AMD products in a legal filing in the 2005 lawsuit.

The FTC's apparent reluctance to investigate Intel was detailed Monday in a New York Times news report. FTC spokeswoman Claudia Bourne Farrell said she couldn't comment.

In August, Sen. Charles Schumer and Rep. Kirsten Gillibrand asked the FTC to probe Intel. A letter to the FTC from the New York Democrats said: "If the allegations against Intel are true, the potential harm to consumers could be profound."

In a response in September, the FTC told legislators the agency is barred by law from disclosing investigations. On Monday, Brian Fallon, a Schumer spokesman, said the agency appears to be "slow-walking" the issue.

Schumer has met with AMD representatives about the company's plans to build a $3 billion semiconductor plant in upstate New York, Fallon and Silverman said.

The FTC may informally look into a company's business practices, but it can only compel a company to turn over documents or other evidence if a formal investigation is under way.

Mulloy said Intel regularly shares information about its business with the FTC. In 1998, the agency alleged that the company coerced several customers into share patented technology. In a 1999 civil agreement settling the charges, Intel was prohibited from taking similar actions in the future.

Intel, which sells more than 75 percent of microprocessors that run computers using Microsoft Corp.'s Windows operating system, has run afoul of competition authorities in Japan and South Korea.

In July, the European Union charged Intel with violating antitrust rules by selling its chips below cost to strategic customers, as well as other practices. Intel has until January to formally respond.

Microsoft, meanwhile, was investigated for violating antitrust law in the late 1990s for similar practices, such as striking deals with computer-makers to exclude rival software. The company remains under U.S. court supervision pursuant to a 2002 antitrust settlement, though that is set to expire Nov. 12.

Silverman wouldn't say Monday whether AMD has petitioned the FTC but did acknowledge that the company had filed a complaint in 2000 in Europe. The company's lawsuit against Intel is scheduled to go to trial in a Delaware federal court in April 2009.

According to a disclosure report filed with Congress, AMD paid a lobbying firm $200,000 in the first half of 2007 to lobby Congress, the White House, U.S. Trade Representative's office and Departments of Commerce and State on "antitrust issues in the semiconductor industry."

AMD shares fell 5 cents to close at $13.75 and Intel shares rose 34 cents, or 1.3 percent, to close at $26.64 Monday.