HOUSTON — Andre Agassi celebrated his first day as the oldest men’s player to be ranked No. 1 in the world with a dramatic comeback victory over Andy Roddick to win the U.S. Men’s Clay Court Championships yesterday.

Agassi supplanted Australian Lleyton Hewitt on Saturday night as No. 1, but he had to work hard Sunday to beat Roddick 3-6, 6-3, 6-4. It was the 58th career title for Agassi.

Down one set and a break in the third game of the second set, Agassi rallied from triple break point to hold his serve. He broke Roddick, the two-time defending champion, in the sixth and eighth games to force the third set.

“I’m still numb, to be honest,” Agassi said. “Andy kept me from getting comfortable for most of the match. Early in the second set, I made some big points and closed out the match. Sometimes it’s better to be lucky.”

Both players stayed on serve in the third set until the fifth game, when Agassi broke through with a backhand drop-shot winner that bounced just over the net.

Agassi also hit a drop-shot winner when he was down love-40 in the crucial third game of the second set.

“I felt pretty desperate the whole time,” Agassi said. “I can understand why it’s so hard to beat him here the way he serves, and his second serve is such a big weapon.”

The big break in the third set was all Agassi needed to boost his match record to 23-1 this season and capture his fourth title of the year, a record that includes the Australian Open.

Agassi declared himself ready for Europe and the clay tournaments, leading up to the start of the French Open on May 26. “You certainly want to know that you have the gears there when you ask for it, and that means physically and mentally,” Agassi said.

“Today was one of those days you try to hold on and hang in there and give you the best chance and hope something goes right. That’s all a part of what’s needed to win big ones.”

Roddick was the stronger player in the first set as Agassi started slowly, hitting numerous unforced errors. He broke Agassi in the eighth game of the first set with a love game. Agassi hit a backhand error at break point.

Agassi survived one break point in the first game of the second set before launching his big comeback in the second game.

Agassi improved to 4-0 against Roddick. Prior yesterday, his last victory over Roddick was 6-3, 6-1 last year in San Jose, Calif.