Brown plays for high stakes in EU treaty talks

By Adrian Croft and Sophie Walker

LONDON (Reuters) - The man with perhaps the most at stake at this week's summit on a new European Union treaty will not be at the negotiating table -- prime minister-in-waiting Gordon Brown.

Europe's leaders meet in Brussels on Thursday and Friday to try to reach agreement on the outline of a treaty reforming the EU's institutions -- a slimmed-down version of a proposed EU constitution rejected by French and Dutch voters in 2005.

The outcome of the summit will be critical to Brown's premiership which begins less than a week later when Prime Minister Tony Blair resigns after a decade and hands over the reins to his long-serving finance minister.

Although Blair will sit at the negotiating table in Brussels for the last time, he is working closely with Brown on the treaty. The two men will discuss the treaty with French President Nicolas Sarkozy in a conference call on Tuesday after Sarkozy cancelled plans to visit London.

Brown, who will become prime minister on June 27, will face the fallout at home from any deal that is reached.

The cautious Brown knows that if the British government is perceived at home as having made too many concessions, it could ignite a firestorm of criticism from Eurosceptics that could have damaging political consequences for him.

"I think the summit is absolutely crucial for Brown. He has to make one of the most crucial choices of his prime ministership even before it begins ...," said Charles Grant, director of the Centre for European Reform, a London-based thinktank.

If Britain agrees to a deal this week, it would give Brown an influential position in Europe but could anger opposition Conservatives, as well as Eurosceptic newspapers whose support he will need at the next election, expected in 2009.