The best sexual intercourse lasts between seven and 13 minutes, according to a new survey by US experts.

According to the research, led by Dr Eric Corty, from the Behrend College in Erie, Pennsylvania, three-minute sex is 'adequate'.

The study is the first to review what the experts believe is the ideal length of time to have penetrative sex, with the random sample of Americans and Canadians labeling seven to 13 minutes most 'desirable'.

The study concluded that intercourse lasting between three and seven minutes was 'adequate', but anything less was 'too short' and beyond 13 minutes was 'too long'.

The extraordinary research is designed to help calm couples' unrealistic beliefs that healthy sex should last a long time.

Corty said that this was a situation "ripe for disappointment and dissatisfaction".

"In the fantasy model of male sexuality, men have large penises, rock-hard erections, and can sustain sexual activity all night long," News.com.au quoted Corty, as saying.

"It appears that many men and women hold this fantasy. The results from the present study, by providing a realistic not a fantasy model of sexuality, are useful both in treating people with sexual concerns and dysfunctions, and with wider circulation, in preventing the onset of sexual dysfunctions," he added.

Reacting to the research, Australian sex therapists commented that most Aussie men wanted sex to last considerably longer while most women were 'not bothered' if it was over with fast.

Dr Jane Howard, a Brisbane-based medical sex therapist, said there was a dearth of data on Australians' expectation of sex.

Anecdotal evidence suggested most Australian women would be happy with the therapists' "adequate" time of three to seven minutes, while men would not.