Diana and Actaeon has been on display at the National Gallery in London as part of the campaign to raise funding
The National Gallery of Scotland and London's National Gallery are poised to reveal whether Titian's Diana and Actaeon has been saved for the nation.
The two institutions are hoping to raise £50m to jointly buy the painting before a deadline of 31 December.
But a spokeswoman for the National Gallery said an announcement would "ideally" be made this week.
The campaign, launched in August, was recently boosted by a £10m pledge from the National Heritage Memorial Fund.
At the time, the galleries said it took them "significantly" closer to their target.
A statement for the National Gallery of Scotland said: "The campaign to save Diana and Actaeon is ongoing. The target has not yet been met. We will make an announcement when we are in a position to do so."
The Scottish Government is also expected to reveal a "significant" pledge to the fund soon.
The painting has been on public display at the National Galleries of Scotland and London for more than 200 years but it is now being sold by its private owner, the Duke of Sutherland.
If the galleries raise the funds to buy Diana and Actaeon, then a second Titian painting - Diana and Callisto - will be offered for sale in four years.
If they fail to raise the required £50m then Diana and Actaeon could be sold to a private buyer.
The two Titians were created as part of a cycle of works for King Philip II of Spain from 1556 to 1559 and form part of the Bridgewater collection, which has been on loan to the National Galleries of Scotland since 1945.
The collection also includes three paintings by Raphael, a Rembrandt, a Van Dyck, and a Tintoretto.
Some newspaper reports have suggested the Scottish Government will give a further £10m to the fund.
A spokesman said: "The Scottish Government recognises the national importance of the Bridgewater Collection to Scotland as the greatest private collection of old masters on loan to a public gallery anywhere in the world.
"That is why we acted decisively, giving the National Galleries a significant funding pledge which was essential to get its fundraising campaign off the ground. We will make a further announcement soon.
"We are determined to do everything we can to ensure that this world-class collection remains on view for visitors and for the enjoyment of the people of Scotland."
Should the two galleries manage to raise the necessary funds, the entire Bridgewater collection will remain on long-term loan to the Scottish gallery.