American Ryan Sweeting launched his title defence at the US Men’s Clay Court Championship on Tuesday with a 6-3 7-6 (8-6) victory over Brazilian qualifier Ricardo Mello.

Sweeting, trailing 5-6 in the second set, saved two set points against his serve as he held on to force the tiebreaker, sealing the win on his fourth match point.

In other matches at the Houston tournament, Tatsuma Ito won an all-Japanese clash with Go Soeda 6-4 7-5 – the first tour-level meeting between the two compatriots.

Ito booked a second-round clash with fourth-seeded Argentine Juan Monaco.

Italy’s Paolo Lorenzi set up a meeting with third-seeded Feliciano Lopez of Spain with a 6-7 (3-7) 6-2 6-3 victory over Wayne Odesnik.

Qualifier Horacio Zeballos booked a marquee second-round clash with America’s Davis Cup hero John Isner via a 6-3 6-3 win over Romanian Adrian Unger.

Isner, seeded second in Houston, delivered two singles victories, including the clinching four-set win over Jo-Wilfried Tsonga, in America’s Davis Cup quarter-final triumph over France in Monte Carlo at the weekend.

Isner had beaten Swiss great Roger Federer on clay in the United States’ 5-0 first-round Davis Cup whitewash of Switzerland in February.

He has also beaten world No.1 Novak Djokovic this year, in the semi-finals of the hardcourt Indian Wells Masters.

“I’m a much more confident player,” said Isner, who flew in late to Houston and is to open his campaign on Thursday after enjoying a first-round bye.

“To be able to compete in this game, you have to be confident and that’s what I have on my side right now.”

Mardy Fish, ranked ninth in the world, one spot in front of Isner, is the top seed in the $US442,500 ($A433,000) event.

In the second round, Fish will face American Michael Russell, a Houston resident who rallied from a set and a break down for a 2-6 7-5 6-1 win over Spain’s Daniel Gimeno-Traver.