BRUSSELS, Belgium?Jose Manuel Barroso may have to wait awhile before he is handed a coveted second term as head of the European Union's executive Commission, despite vocal support from most European Union leaders.

Barroso's chances of securing a fresh mandate were boosted last week when his fellow conservatives came out on top in European parliamentary elections across the 27-nation bloc.

The issue will be at the center of an EU summit in Brussels this week where the former Portuguese prime minister had hoped to be formally re-anointed.

Barroso's mandate expires in October, but he is seeking a second term despite the EU's struggle to reform and criticism of his commission's response to the financial crisis.

He has sought to placate critics by promising "an ambitious program" over the next five years, including tougher supervision of banks and tackling climate change.

His path would appear to be clear. He has won support from numerous heads of state and government and is so far the only real candidate.

Last week France and Germany threw their weight behind a second term for Barroso, but said he must commit to a clear plan for steering Europe forward.

After meeting with German Chancellor Angela Merkel at the Elysee palace, French President Nicolas Sarkozy said: "We will support the candidacy of Barroso, without ambiguity."

But the leaders agreed to ask Barroso to outline his agenda as Europe battles its worst recession in decades.

There's also an institutional hurdle to be overcome due to the fact that the EU's reforming Lisbon Treaty, which would change the make-up of the commission, is not in place but should be soon.

If Barroso is chosen now, his reselection could be endorsed by the new EU parliament next month on the basis of the existing Nice Treaty, with a simple majority of those in the chamber.

But other nations may cry foul as Portugal would thus be assured an EU commissioner whereas under the Lisbon Treaty not all nations will secure one.

If however the process is delayed until after the new treaty is finally ratified, when Irish voters who rejected it last year are asked the question again in October, then Barroso would need support from an absolute majority of the 736-member house, rather than just of those present.

The third way, according to diplomats, would be for EU leaders to give him political support in principle at their summit this week, as France and Germany have mooted.

French President Nicolas Sarkozy seemed last week to think the process could be straight-forward enough, suggesting that Barroso's reappointment could be ratified by the new European parliament when it meets for the first time next month.

However the parliament is unlikely to accept this ad hoc solution, sources say, with resistance even from the European People's Party?the umbrella grouping of national conservative parties which came out on top at the polls.

Without the formal blessing of the European leaders "we couldn't vote in mid-July" the EPP's French president Joseph Daul told AFP.

As for the socialist MEPs, they want a nomination late in the year, to avoid complications with the Lisbon Treaty.

Behind the byzantine Brussels procedures lies a more basic political game.

Keeping Barroso in a state of uncertainty would allow powerful EU countries such as France and Germany to seek out plum commission posts for their own nations. France in particular would like the internal market portfolio, diplomats said.

There is also the question of the program of the future commission, tasked with drawing up European legislation and policing the existing rules.

"His duty is to protect and ensure that Europe protects Europeans and to commit to work toward improving financial regulation as we have decided," Sarkozy said after the Paris talks with Merkel.

Merkel also stressed that Barroso must have the right game plan.

Neither does Barroso enjoy unanimous backing.

Green party leader Daniel Cohn-Bendit, along with some liberal figures, favor an anti-Barroso front with the socialists.