French President Jacques Chirac has called in the leaders of Germany and Poland to boost his campaign for France to back the European Constitution.
The three leaders are pushing hard for a "yes" vote
Polish President Aleksander Kwasniewski and German Chancellor Gerhard Schroeder joined Mr Chirac in backing a "Yes" vote in the 29 May referendum.
The move is part of an all-out effort to convince sceptical French voters.
As part of the campaign, Mr Chirac also called for a review of the UK's rebate, now worth 4.6bn euros ($5.8bn; £3.2bn).
The UK won the rebate on its contribution to European Union funds in 1984 after a campaign by then Prime Minister Margaret Thatcher.
But Mr Chirac said Germany, France and Poland agreed that the need for EU budget discipline and fairness to the EU's 10 new members meant that it was time to think again.
"We concluded that to be able to incorporate all these demands (on the budget), we need to have a fairer financing of the European budget... which would incontestably demand looking again at the British rebate," he said.
British officials have said the UK pays more than twice as much as France does even after the rebate, given France's big receipts from the Common Agricultural Policy.
Thursday's demand was the second time in less than a week that Mr Chirac has used the rebate as a weapon in his campaign to get a "Yes" in Sunday's vote.
Recent polls have suggested that the "No" camp is ahead.
But the leaders gathered in Nancy were keen to back the campaign with other arguments as well.
Chancellor Schroeder warned that a "No" vote would mean the end of the constitution - not the chance to rewrite it.
"France assumes a big responsibility, the responsibility not to let us other Europeans down as to what concerns the constitution," he said.
"Believe me, I say it clearly: there's not the slightest chance of reopening the constitutional process."
German MPs backed the referendum - which must be approved by all 25 members to take effect - in a parliamentary vote earlier in May.
Poland, Mr Kwasniewski said, needed a French "Yes" vote too.
"I wish for myself, for all of us, that this constitutional treaty will be adopted here," he told a news conference.
"It will be a very important sign for the Polish referendum" in October, he said.