The National Gallery has been in talks with the Art Fund to avoid the loss of a number of significant works, potentially to private collections overseas, Museums Journal can reveal.

Currently on loan to the gallery, Rubens' Apotheosis of King James I, owned by Viscount Hampden's family trust, and Poussin's Sacraments, owned by the Duke of Rutland, are both being offered for sale. Titian's Portrait of a Young Man, which has been loaned to the gallery by Lord Halifax since 1992, was withdrawn two years ago and is now also for sale.

David Barrie, the director of the Art Fund, said he has had 'many conversations' with the National Gallery, but that the gallery had not made a formal request for assistance, as it had not yet formulated its strategy.

Although the gallery has looked at purchasing the Titian, it has not been able to reach an agreement on the asking price, estimated to be in the region of £10m-£15m. It is understood that it will not attempt to purchase the Rubens but will focus its attention on Poussin's Sacraments, a series of five paintings that have been in the UK for more than 200 years. They have an estimated market value of more than £100m.

Robert Holden, the Savile Row art agent acting for the Duke of Rutland, confirmed that he was 'in discussion with the National Gallery about the long-term future of the paintings'.

However, there are fears that the gallery may not be able to afford them. Barrie told Museums Journal: 'The National Gallery has the Paul Getty endowment, but it is not enough to pursue an ambitious acquisitions programme, and the Poussin paintings are so expensive that the Art Fund could only offer symbolic help.'

Meanwhile the Rubens may remain in the country if an agreement can be reached between Viscount Hampden and the Tate. A spokeswoman for Tate Britain said: 'Tate Britain, as the national gallery of British art, has expressed a strong interest in finding ways of keeping this important work on public display.'

The situation is exacerbated by the National Gallery's loss of its director, Charles Saumarez Smith, who left at the end of July to become the secretary and chief executive of the Royal Academy of Arts in September. The gallery's former director of conservation, Martin Wyld, has become the acting director.

In his time as director, Saumarez Smith was vocal about the lack of acquisition funds available to the gallery, telling the Culture, Media and Sport select committee in October last year: 'Private owners are taking the view that their primary responsibility is towards maintaining their estate, therefore works of art which they have had for many generations are now going on sale.'