NEW YORK (AP) - A family trust is suing Christie's for failing to pay $40 million it guaranteed for the sale of a 1964 Francis Bacon painting that never sold.

The lawsuit claims that Christie's got the Irish artist's painting ‘‘Study for Self Portrait'' from Weiss Family Art and, in competition with Sotheby's, promised the seller $40 million regardless of the sale's outcome.

When the bids dried up at just over $27 million, the sale of the painting was halted. Christie's said it would no longer honor the guarantee because of the faltering economy.

Only six months earlier, a Bacon triptych fetched $86 million, a record for the painter.