PAriS — An Anglo-French plan for a new generation of nuclear power stations will be unveiled by President Sarkozy of France and Prime Minister Brown of Britain this week as part of a series of measures designed to forge a “fraternal” relationship between the two countries.

Mr. Sarkozy, who arrives on Wednesday for the first full state visit by a French president for 12 years, is to offer French expertise to help Britain build replacement nuclear reactors for its ageing plants, responsible for 20%of electricity production.

The two countries will then work together to export the advanced technology abroad.

The joint effort will be hailed as a drive to reduce greenhouse gas emissions by reducing Britain’s reliance on fossil fuels. But antinuclear campaigners are expected to react with dismay to the notion that Britain may follow the lead of France, which generates 80% of its electricity from nuclear energy.

Mr. Sarkozy is also preparing to tell Mr. Brown that France will send up to 1,000 additional troops to Afghanistan to demonstrate his commitment to the NATO mission in the country, although a formal announcement may be delayed until next month’s NATO summit in Romania.

He has already signalled his desire to bring France back into NATO’s command structure, ending the semi-detached status insisted on by President Charles de Gaulle four decades ago. In return, Mr. Sarkozy is seeking both British and American support for the European Union to build up its defense capability within NATO.

However, in a report to be published today, a Washington think-tank says that the move could “tear Nato in half.” The Heritage Foundation warning comes as the US seems willing to back the French plans so that Europe can make a greater contribution to the war on terror.

The critical American report concludes: “The ransom being demanded by Paris for a return to the Nato fold is too high a price for the United States and great Britain to pay.”