In a bid to capture the surging popularity of motor sports, Donald J. Trump has formed a partnership with the president of Nascar to build a major speedway on up to 1,000 acres in the Catskills, northern New Jersey or Connecticut.

Mr. Trump and the Nascar president, William J. France, who is also the chairman of the International Speedway Corporation, have identified a number of potential sites in the New York metropolitan region for the raceway, which is expected to cost up to $400 million and seat as many as 300,000 fans, according to executives on both sides of the deal.

The track, like many of the developer's buildings, would bear his name: Trump Super Speedway.

''It'll be the tallest building in the world sideways,'' said an executive involved with the Trump Organization, who spoke on the condition of anonymity.

The two men signed a deal yesterday at Trump Tower on Fifth Avenue, the executives said. The International Speedway Corporation and the Trump Organization are to announce the venture at a news conference at Trump Tower today