Jose Luis Rodriguez Zapatero, sworn in as Spanish prime minister yesterday after a shock election victory, must now juggle his supporters' expectations for change with the realities of politics.

Zapatero ousted the pro-US, conservative Popular Party in last month's elections held days after suspected Al-Qaeda-linked train bombings that killed 191 people, benefiting from a voter backlash against the Popular Party's handling of the attacks.

Since then, the 43-year-old career politician has stood by his campaign pledge to withdraw Spain's 1,300 troops from Iraq if the United Nations does not take charge there by June 30.

He was a strident critic of the Iraq war and even after the elections maintained an undiplomatic tone about US policy, calling the Iraq war a fiasco and urging President George W. Bush to take a long hard look at himself.

Now in power, he will have to choose between risking the wrath of the world's only superpower by pulling out the troops from Iraq or alienating his supporters if he leaves them there.

Zapatero hopes to remain on friendly terms with the United States, while mending relations with France and Germany that were strained by former Prime Minister Jose Maria Aznar's strong support for the war in Iraq.

Whereas Aznar dug in his heels over the proposed European Union constitution, refusing to see Spain's voting power trimmed, Zapatero wants a new charter signed by the middle of this year. That will almost certainly mean compromise for Spain.

At home Zapatero - who has an endearing grin and winks warmly at supporters - has pledged a new style of politics with "dialogue" one of his favourite words.

Criticised for a lack of aggression in opposition, his willingness to compromise will be essential in government.

Voters handed the Socialists 164 seats in parliament, 12 short of an absolute majority, so Zapatero will be reliant on support from smaller parties to push through his programme.

Zapatero won parliamentary approval to become prime minister with the help of regional parties and a left-wing group.

One of those parties is the Republican Left of Catalonia which sparked controversy this year when its leader - then number two in a coalition government with the Socialists in Catalonia - admitted he had met armed Basque separatists ETA.

Zapatero's pledge to try to make Catalan an official EU language could be a sign of bargaining to come with regional parties keen for more independence from Madrid.

He will have to review security and intelligence services, clearly caught off guard by the March 11 attacks, that the authorities initially blamed on Basque separatist guerillas rather than Islamic militants.

He has also made an ambitious promise to tackle the problem of expensive housing for young families by making available 180,000 affordable houses a year. Zapatero seems easy-going but people who know him say he should not be under-estimated.

"He is a 15-round fighter, the kind that gets into trouble in the first four rounds, and then gradually takes over," Manuel Garcia, his former law professor, told El Pais newspaper.

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