Zoo keepers hope the UK's only giant panda couple will mate today after female Tian Tian spurned her partner in favour of sleep.

Tian Tian and Yang Guang, residents of Edinburgh Zoo, are primed for breeding but an encounter yesterday did not produce the desired result.

Animal experts said sleepy Tian Tian (Sweetie) was not quite at her peak but the pandas will be reunited today to see if she is in the mood.

A zoo spokeswoman said last night: "Another enclosure swap will take place - Tian Tian will go into Yang Guang's outdoor enclosure and vice versa.

"This will give us the perfect opportunity to again monitor what stage Tian Tian has then reached. We hope she will continue to progress overnight and fully hit peak tomorrow morning."

Tian Tian and Yang Guang (Sunshine) arrived from China in December 2011 and were introduced to each other before last year's breeding season but did not mate.

Signs that Tian Tian is once again in season include grumpy behaviour and loss of appetite.

She will only have a 36-hour breeding window and during that time the pandas will meet up to three times a day for 15 to 30-minute intervals.

She will also be artificially inseminated to increase her chances of getting pregnant.

Iain Valentine, director of giant pandas for the Royal Zoological Society of Scotland (RZSS) which owns the zoo, said: "We are hopeful as the breeding season of both bears seems to be really in sync this year.

"However, nothing is a foregone conclusion with giant pandas and with pregnancy in general. Not every successful mating leads to pregnancy."

Tian Tian and Yang Guang are the first giant pandas to live in the UK for 17 years.

If Tian Tian becomes pregnant, confirmation will come in mid-July when experts can carry out an ultrasound scan. It would then be likely that her cub or cubs would be born at the end of August or the beginning of September.

The normal breeding season for pandas is mid-April to May.