Zapatero said on Monday that Spain would host a first high-level meeting in the Balearic Islands.
The Socialist leader first mooted the idea after coming to power in April last year in a bid to bring Western and Muslim countries together and overcome mutual misunderstandings caused by issues such as the war in Iraq.
Zapatero strongly opposed the conflict and within weeks of taking office withdrew Spanish troops sent to Iraq in August 2003 by the government of his conservative predecessor Jose Maria Aznar.
Last week, British Prime Minister Tony Blair met Zapatero in London and afterwards welcomed the proposal, which aims to create, in the British leader's words, a "coalition of civilised people from whatever race or religion to combat the barbarity of terrorism".
Spain's capital Madrid saw a deadly attack on its railway network on 11 March 2004.
It has also suffered decades of separatist Basque violence, which has re-emerged this year, with the armed separatist group ETA staging more than a dozen non-lethal attacks and regular street violence involving pro-ETA youths since Spain's Socialist government announced in May that it would hold talks with the group if it renounced violence.