France and the UK are to set up a joint nuclear energy forum, French President Jacques Chirac has announced at a summit with Tony Blair in Paris.
Relations between Mr Blair and Mr Chirac are more harmonious now
The two countries will share expertise - bringing together ministers, businesses and industry experts.
Also on the agenda was a common defence policy, European enlargement and Iran.
Mr Chirac said he was delighted to report a sense of solidarity and agreement. The upbeat mood contrasted with the summit atmosphere a year ago.
When the two leaders met in Paris last June, disagreement over the EU budget - especially farming subsidies - was so strong, Mr Blair was left holding a news conference on his own.
This could be one of the leaders' last bilateral summits, with France already preparing for elections next April.
The UK generates far less of its electricity from nuclear power than France - about 20%, compared with 80% in France.
Mr Blair said France's long tradition of nuclear power meant it was a good opportunity to co-operate and learn from each other.
"We have agreed to explore in the short term and further develop the opportunities of working together in the civil nuclear field," the two leaders said in a joint statement following the talks.
"To that end we have agreed to establish a regular Franco-British Nuclear Forum, involving representatives from government, industry and technical experts.
"The Forum will provide a vehicle to discuss Franco-British nuclear co-operation, including research, skills, decommissioning and waste management."
Mr Blair told a joint news conference he was not prejudging the outcome of his government's upcoming energy review, but said he believed it was a simple question of energy efficiency, self-sufficiency and climate change.
He said there would be a big problem if the UK were unable to replace nuclear power stations due to become redundant within the next 15 years.
Mr Blair said energy security and climate change were the two things that had "pushed our two countries towards an energy policy as a major factor in our own politics, domestically but also in European politics".
When asked about Iran's nuclear programme, Mr Chirac said they could not accept any Iranian effort to build a nuclear weapon.
"We cannot accept that it has launched and pursued a process that could, notably through enrichment... lead to the creation of a nuclear weapon," he said.
Other issues discussed at the summit included Afghanistan, the Middle East and proposals to create a World Bank fund to pay the salaries of Palestinian officials.
France and the UK also plan to work more closely on defence projects. Mr Chirac said he hoped a joint aircraft-carrier programme could begin next year.
The BBC's Caroline Wyatt, in Paris, says both Mr Chirac and Mr Blair are seen as leaders in their last term in office and both seem determined to focus on what unites rather than divides their two nations.
The storms that once characterised their relationship appear to have abated - perhaps leading to an unusually serene last summit in Paris.