"We'll take it to the European Commission in the first instance, but to the Court of Justice ultimately if we're not happy with its decision," a spokesman for the Department of the Marine & Natural Resources told Reuters.

Spain said last week's agreement enshrined its right to fish inside the "Irish box" that forms a rectangle extending for up to 80 miles around the island.

"The agreement recognises the right of Spain and Portugal to fish in community waters," said a spokesman for Spain's agriculture and fishing ministry.

He added he expected 200 Spanish ships, mainly from the Cantabrian area of northern Spain, to take advantage of unfettered access to the 'box'.

The existing agreement, which European Commission legal experts said expires on December 31, limits access to only 40 Spanish vessels at any time.

WAR ON THE SEAS

Irish Minister for the Marine and Natural Resources, Dermot Ahern said he hoped the dispute would not lead to "a war on the seas" but fishing groups have warned of violent clashes between Irish and Spanish boats.

"There would be a lot of conflict on the fishing grounds and that could be dangerous," said Lorcan O'Cinneide of the Irish Fish Producers' Organisation.

Manager of Irish South & West Fish Producers' Organisation Jason Whooley said Irish fishermen might cut through Spanish nets.

"I can see a situation where (our) members are not prepared to manoeuvre around them," he said.

Irish fishermen say the smaller size of the boats in the Irish fishing fleet means they are unable to take advantage of unrestricted access to Spanish waters.

"These (larger Spanish) boats will fish these waters out in a couple of years and where will we be then? We can't go anywhere else," O'Cinneide said.

(Additional reporting by Daniel Flynn in Madrid).