John Lennon wrote Imagine on the upright piano in 1971

Michael bought the piano, which is an upright model and not the white grand seen in the video for Imagine, for �1.67m at an auction in 2000.

It will leave the UK for the first time to appear at the exhibition in Dallas.

The show will also feature pictures taken by war photographer Don McCullin in Afghanistan, Vietnam and Beirut.

It will be held at Goss's own gallery, which opened in Dallas last year.

Goss told the Reuters news agency there was "no better place to reiterate how important peace is".

"Dallas is George Bush's home. It's a great place to remind people how important it is that we find peace."

Drug storm

George Michael recently embarked on his first tour in 15 years

Michael has recently drawn criticism for being filmed smoking cannabis on a special edition of ITV's South Bank Show.

In the programme, the former Wham frontman, 43, is seen lighting what appears to be a cannabis joint and saying: "This stuff keeps me sane and happy."

Mental health charity Rethink called the singer's actions "stupid" and "naive".

The documentary attracted two million viewers when it screened on ITV on Tuesday, according to provisional overnight figures.

Michael has been found slumped at the wheel of his car twice this year. He was cautioned by police for possessing cannabis after the most recent incident in October.

The singer recently embarked on his first live tour for more than 15 years, with the UK leg due to begin later this month.

Earlier this year, he denied that Goss had called off a civil partnership ceremony over reports he has "cruised" for sex with strangers.

"With all the rubbish I've had to put up with in the last six months, we wouldn't get a small private wedding, which is what we want," he told Channel 4 daytime presenters Richard Madeley and Judy Finnigan.