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Delgado, who had to qualify for the tournament, saved a match point in the second set before fighting to a 5-7 7-5 7-6 victory over the American.

The Briton, ranked 326th in the world, said: "It's an unbelievable win."

He will meet countryman Jonathan Marray, who beat Belgium's Christophe Rochus 6-3 4-6 7-5.

Delgado, who is ranked 294 places below Dent, added: "It shows me that I can still play well and hopefully have my best years ahead of me.

This is great for the confidence but I have to build on it and get back to where I think I should be Jamie Delgado

"I think I should be ranked higher than where I am and I am capable of more. Once I got into the match I started to believe I could win it and once it went to the third set I really felt the match would be mine.

"For me, a win like this is great for the confidence but I have to build on it and get back to where I think I should be."

Delgado missed out on a Wimbledon wildcard but will try to earn one through the LTA's new play-off tournament later this week.

"Wimbledon for me is the biggest tournament in the world so I am gagging to be there," added Delgado, who qualified through the play-off last year and took a set off Andre Agassi in the first round.

"I think it's fair that guys like me whose rankings are low have to earn the right to be there."

I played well and stuck to my game plan, which was to basically come in behind virtually anything Jonathan Marray

The 23-year-old Marray, ranked 277th in the world, looked to have blown his chance when he wasted two break points at the start of the second set, but he broke back early in the decider.

The Briton, guaranteed a �4,552 pay day for the result, had never previously won a match on the ATP Tour - he qualified for the Nottingham Open last year but lost in the first round.

The delighted Sheffield player said: "This is probably my best win against a player ranked so high (115th) in the world.

"I only found out I got the wildcard on Thursday evening and it's good to do something with it.

"I played well and stuck to my game plan, which was to basically come in behind virtually anything."

British number three Arvind Parmar lost to Canadian Frank Dancevic.

Parmar led 5-2 in the first set before losing it 7-5, but raced through the second set 6-1 to set up a decider.

He went a break up early on, but Dancevic, who also beat Greg Rusedski at Surbiton last week, hit back to level and took the match on the tie-break, winning 7-5 1-6 7-6 (7/5).

In other matches, giant 14th seed Ivo Karlovic of Croatia beat America's Jan-Michael Gambill 6-4 6-7 (5/7) 7-6 (7/5).

And Frenchman Olivier Patience saw off Spanish 13th seed David Ferrer 4-6 7-6 (7/2) 6-4.