VERSAILLES, July 21, 2008 (AFP) - French lawmakers gathered Monday for what was set to be a tight vote on President Nicolas Sarkozy's plans to rewrite the constitution, with opposition Socialists warning the project would turn France into a 'monocracy.'

The bill would set a two-term limit for presidents, give parliament a veto over some presidential appointments, end government control over parliament's committee system and allow parliament to set its own agenda.

But the clause that has dominated public debate is one that would let the president address parliament, which the head of state has been barred from doing since 1875 to ensure the executive and legislative are kept separate.

Socialist senator and former justice minister Robert Badinter said the reform would be the equivalent of crowning Sarkozy king.

If the president addresses parliament directly, in a French-style state of the union address, 'what happens to the prime minister in that case, all small on his bench next to his silent ministers?'

'It's 'monocracy,' the power of a single man,' he said last week.

But rightwinger Sarkozy has argued that his reform of the constitution -- which was brought in by president Charles de Gaulle in 1958 and gives the president sweeping powers -- grants more weight to France's weak parliament.

He said the changes -- a key promise in the election campaign that brought him to power a year ago -- make the head of state more accountable to lawmakers and to the public.

'If this reform fails, it will be a failure for everyone, first and foremost for democracy, for parliament and for the rights of citizens,' Sarkozy warned in a recent interview with Le Monde newspaper.

But on Monday it looked far from certain that the bill, which would also end the right of collective pardon currently enjoyed by the president, would pass.

It must get a three-fifths majority and Sarkozy is thus dependent on cross-party support as the 330 members of the Senate and 576 deputies of the lower-house National Assembly meet in the chateau of Versailles -- the former residence of French kings -- for a so-called congress to vote on the project.

Sarkozy spent the weekend with his pop star wife Carla on a break in the Moroccan city of Marrakesh, but, according to various sources, he has been working the phones to try to win over wavering members of his own UMP party and other politicians whose support is crucial.

Despite last-minute concessions, the Socialists, the Greens and the Communists have all said they will vote against.

The result of the congress could depend on as little as two or three votes.

Jack Lang, a member of a cross-party commission that laid the groundwork for the constitutional reform, is the only Socialist who says he will vote for the bill.

The Socialists had asked for guarantees of equal time on national television to counterbalance the president's new right to address the parliament.

They also demanded a change to the election of senators, who are chosen by local councillors and deputies, with some Socialists seeking a system of proportional representation.

The result of Monday's vote was expected around 1800 GMT.