Cameron defends EU deal as lawmakers offer no guarantees

* British PM meets Juncker, EU parliament leaders in Brussels

* Hoping for pre-referendum deal at summit starting on Thursday

* Summit chair says leaders will need to go 'extra mile'

* France pressing over banks, east over welfare curbs (Adds Cameron, Sobotka, edits throughout)

By Alastair Macdonald

BRUSSELS, Feb 16 (Reuters) - David Cameron fended off changes on Tuesday to a draft deal he has cut to help keep Britain in the EU, as other states demanded adjustments and the European Parliament said it could not guarantee to pass the reforms.

After talks on Monday with President Francois Hollande, who argued the draft text may give British banks unfair advantages, the British prime minister visited Brussels to meet EU executive chief Jean-Claude Juncker and leaders of the EU legislature.

Two days before a summit where all sides hope for agreement, wrangling continued behind the scenes over the wording of the deal. Cameron made no public comment during his stay in Brussels and one person who met him said he appeared "very stressed".

But Manfred Weber, the parliamentary centre-right leader and an ally of German Chancellor Angela Merkel, said he seemed "strongly convinced that he can convince the people" to maintain EU membership in a referendum EU officials expect Cameron to call soon after the summit, probably scheduled for June.

Summit chairman Donald Tusk, who presented a plan two weeks ago to help Cameron campaign on the basis the EU was adapting to British tastes, said after he met the Czech prime minister in Prague that leaders would have to go "an extra mile".

Bohuslav Sobotka said poorer states feared that not just Britain might use new rights to cut benefits for migrant workers from the east of the bloc.

Unhelpfully for Cameron as he faces scorn from eurosceptic opponents who say his deal is unlikely to survive a necessary passage through the European Parliament, the assembly's president said he could not guarantee to deliver new laws on benefits and migration after Britons have voted.

"This is not possible in a democracy," Martin Schulz said -- though he also said parliament had "no veto" over the accord and he, Weber and other leaders of major parties said they would legislate within the "framework" of the deal.

Cameron insists any agreement will be legally binding, even if it does not change EU treaties but takes the form of a treaty among the 28 EU states on how to interpret existing rules.

His office issued a statement saying party leaders he met supported the proposals and assured the prime minister they were ready to pass the necessary legislation after the referendum.

"MONKEYS WITH GUNS"

But parliamentary leaders are concerned that cutting deals for London will encourage others to seek favours, raising the prospect of cross-party, transnational haggling in the assembly.

"It (Other OTC: ITGL - news) 's Pandora (LSE: 0NQC.L - news) 's box," one parliamentary official said. "The parliament is unpredictable. It can be monkeys with guns."

Before reaching that stage, however, diplomats and officials still have to hammer out a final draft for leaders to discuss on Thursday and Friday. France still wants guarantees that wording intended to ensure the City of London (LSE: CIN.L - news) does not suffer from deals cut within the euro zone does not then allow British banks a chance to benefit from lighter local regulatory constraints.

Diplomats said British officials have been defending Tusk's draft against efforts to chip away at Britain's gains but that, given the lukewarm reception in Britain for his reforms, Cameron may also try to secure new concessions in the final days.

Easterners are focusing on limiting how many years Britain can apply the new "emergency brake" on benefits.

More generally, many governments which favour a more federal Europe want clarity that language to reassure Britons they need not integrate deeper with the EU does not also apply to others.

All the 27 other leaders say they want to help keep the EU's second biggest economy inside, however, and are keen to move quickly on to the summit's other main issue, Europe's migration crisis. (Additional reporting by Robert-Jan Bartunek and Philip Blenkinsop in Brussels, Paul Taylor in Paris, Jan Lopatka in Prague and Kylie MacLellan in London; editing by John Stonestreet)