PORTLAND – The Boston Red Sox on Friday announced a four-year extension of its player development contract with the Portland Sea Dogs, a Double-A team in the Eastern League.

The agreement, announced at a news conference at Hadlock Field, ensures that the Sea Dogs will be affiliated with the Red Sox through 2008. The four-year extension is the longest permitted.

“We’re excited to continue our relationship with Portland and build on the success we’ve had over the last two years,” said Ben Cherington, Red Sox director of player development.

“Portland is our northern extension of Red Sox Nation and an integral part of our Red Sox player development triumvirate in New England, along with Triple-A Pawtucket and Single-A Lowell,” he said.

Red Sox general manager Theo Epstein joined Sea Dogs President Charlie Eshbach for the announcement.

The Sea Dogs began their relationship with the Sox in September 2002 after nine years with the Florida Marlins.

Upon changing affiliations in 2003, the Sea Dogs erected a likeness of Fenway Park’s Green Monster in left field. The skyboxes at Hadlock Field were renamed for former Red Sox legendary hitters.