"I've always said that if being a Democrat hurt my district I would switch or I would resign," Hall said in an interview with The Associated Press. He said GOP leaders had recently refused to place money for his district in a spending bill and "the only reason I was given was I was a Democrat."

In an interview in which he said he had filed to run as a Republican, he also said he didn't agree with "all these guys running against the president."

Hall's switch follows a GOP-led drive - bitterly contested by Democrats - to remake Texas' congressional districts more to their liking. Party strategists contend they can gain five or more seats through a mid-decade redistricting, a change that could greatly strengthen their grip on power in the House.

Before Hall's move, the House had 228 Republicans, 205 Democrats, 1 Democrat-leaning independent and 1 vacancy.

In addition to representing a personal change, Hall's defection had historic overtones. His district in Texas includes territory once represented in Congress by the late Sam Rayburn, who served as a Democratic speaker for much of the time between 1940 and 1961.

House Speaker Dennis Hastert, R-Ill., said he looked forward to working with Hall in the majority party.

"Ralph is a man of courage and a man of great conviction," Hastert said. "Common sense continues to guide him in Washington and now in the Republican Party."

Fellow Texan Tom DeLay, the House majority leader, called Hall on Friday to welcome him to the party.

"Democrats are reaping what they've sown," DeLay said. "Their leaders have lined up behind Howard Dean's brand of angry, intolerant politics. They've made their message clear: 'moderates need not apply' and that's a sad trend for a once-great party."

President Bush also praised Hall.

"I welcome Congressman Ralph Hall to the Republican Party," Bush said. "Ralph is a close friend of the Bush family. He is a well-respected leader of the highest integrity, and a tireless advocate for the people of Texas."

Rep. Martin Frost, Texas' most senior Democrat, declined comment late Friday.

Republican sources, speaking on condition of anonymity, said Hall privately relayed word of his intentions to White House officials and other senior GOP officials earlier in the day.

Hall, 80, was first elected to the House in 1980.

Hall has long been among the most conservative Democrats in Congress. Speculation that he might switch parties first surfaced in 1995, when the GOP gained control of the House for the first time in 40 years.

He said then he wouldn't, arguing that it would be better to try and move the Democratic party toward the middle.

Hall's sons, one a Texas judge and the other a lawyer, had been considered possible candidates for their father's congressional seats if Hall resigned. Hall said Friday his party switch would make it easier for his sons to run should he eventually resign, but he added, "Neither of my sons seems interested in coming to Congress."

Democrats have sued to block the new redistricting plan, arguing it violates minority rights. The Justice Department has approved the plan, and a court ruling on its legality is expected shortly.

Texas Republican Party spokesman Ted Royer said Hall was the 174th elected Texas Democrat to join the Republican Party since 1992.