The painting has been on loan at the National Gallery since 1992

The current owner of Raphael's Madonna of the Pinks, the Duke of Northumberland, has agreed to sell the painting to a US gallery to prop up his estate's ailing finances.

But he is giving the National Gallery - where the painting has been on loan for the last decade - one last chance to keep it.

The duke's Northumberland Estates rely on farming for most of its income, but has been hit by the foot and mouth crisis and other rural problems.

Madonna of the Pinks, painted in the early 16th Century, is described as "one of the greatest old master paintings still in private hands in Britain" by the National Gallery.

The National Gallery says it is hampered by the lack of government funds

"It would be a very serious loss to the nation should it leave the country," a statement said.

The gallery has applied for £20m of lottery money and aims to raise the rest from private donors.

The Duke of Northumberland did not have a formal arrangement with the gallery to let it keep the painting, a spokesman for Northumberland Estates told BBC News Online.

The duke said: "Though we shall be very sad to lose this picture we are glad that it will continue to be available for the public to see.

"Its sale will enable us to continue to preserve our heritage and invest in projects aimed at improving life, culture and employment in Northumberland."

The painting previously hung in Alnwick Castle, Northumberland

If the National Gallery does not find the money, the painting is likely to be sold to the J Paul Getty Museum in Los Angeles, who say they have arranged a $50m (£32m) fee.

But Northumberland Estates "very definitely" want it to stay in the UK if possible.

"The Getty Trust's offer has been accepted, but we're also giving a British institution another chance to make a similar offer," the Northumberland Estates spokesman said.

"We've decided that to safeguard the estate for the future, the sensible thing is to sell the painting and invest the money in other ways."

The money would be spent on farm diversification projects, the garden and "keeping the rural economy of Northumberland going for the future".

'Fake'

Northumberland Estates owns 3,000 acres of land, with 200 tenant farmers and 300 employees.

It also runs two stately homes - Alnwick Castle in Northumberland and Syon House in London.

Madonna of the Pinks was bought by Algernon, the fourth Duke of Northumberland, in 1853.

It was later dismissed as a fake - but rediscovered when it caught the eye of a National Gallery expert, who saw it in a corridor in Alnwick Castle in 1991.