Pattinson, Stewart have incredible chemistry, says co-star

British actor Robert Pattinson and American actress Kristen Stewart are said to have an undeniable chemistry between them.

Pattinson, 23, and Stewart, 19, have worked together in the Twilight sequel New Moon, and their co-star Ashley Greene, who joined the duo at Comic-Con in San Diego to promote the new film, says the two just sizzle.

"The chemistry is incredible," People magazine quoted Greene as saying.

The two stars reunited on July 23 at the convention after spending most of the summer on different coasts, with Stewart in LA filming The Runaways, and Pattinson in New York City filming indie drama Remember Me.

New Moon screenwriter Melissa Rosenberg praised the two as "genuine" and "authentic" people.

"They're just people you can feel like you can relate to them," Rosenberg said.

"That sets them apart in a lot of ways," she added.

The co-stars will start filming Eclipse, the third instalment in the series, in August.