"We will deploy the necessary effort to achieve this project or at least put it on the right track," Moroccan Prime Minister Driss Jettou said.

Spanish Prime Minister Jose Luis Rodriguez Zapatero, who completed a two-day official visit to Rabat overnight, shared Mr Jettou's optimism and called the plan an "historic project".

Mr Zapatero pledged to drum up European Union support for a project he said "would change Africa and Europe".

"The fixed link would bind the African continent to Europe.

It is an ambitious project but we are sure it is within our reach," Mr Jettou said.

Moroccan authorities displayed blueprints of the project.

Engineers say one of the most daunting obstacles in building the tunnel is the seabed under the Strait of Gibraltar, which is more permeable than it is around the Channel Tunnel.

This would mean boring further down, pushing costs higher.

Neither Mr Jettou nor Mr Zapatero estimated the cost. Expert forecasts have ranged between $US7 billion ($9.1 billion) and $US17 billion ($22.09 billion).

Support for the project reflected how warm ties between Rabat and Madrid have become under Mr Zapatero's Socialist government. Four cooperation accords were also signed, including one on cracking down on illegal migration of children.

Relations had soured under conservative former Prime Minister Jose Maria Aznar over illegal migration, drug trafficking and the disputed territory of Western Sahara. Mr Zapatero replaced Mr Aznar in 2004.

Mr Zapatero cited a 60 per cent drop in illegal migration from Morocco and increases in trade and investment as among fruits reaped from "excellent relations" between the two countries.

Spain is Morocco's second trading partner after France and its second source of foreign investment, with about 1000 Spanish companies present in sectors ranging from energy to tourism, real estate and agriculture