Bono said the troops would spend 90 days in Pakistan as part of a NATO relief force following the quake which killed some 54,000 people and left millions more homeless.

Calling the situation in Pakistan "dramatic," Bono said that the troops would leave only after parliament had given its approval.

Lawmakers were due to vote on the issue later Wednesday, the Socialist government last March having passed a law deeming that such missions required parliament's express approval.

That decision came two years after former conservative prime minister Jose Maria Aznar sent Spanish soldiers to Iraq to back the US-led intervention without consulting parliament, a move which enraged more than four fifths of the electorate.

One of the first moves by the current government was to withdraw the troops.

NATO agreed on Friday to send some 1,000 troops to help reconstruction efforts.

Although the new Spanish law has yet to take full effect, Spanish Prime Minister Jose Luis Rodriguez Zapatero called for it to be put into practice with the earlier deployment of a Spanish contingent in Afghanistan.

The law forsees Spanish missions in the context of proposals voted by the UN Security Council or international organisations such as the European Union or NATO.