Washington — The United States on Wednesday rejected international recognition for breakaway Somaliland and called for calm after the region's leaders signed a deal with Ethiopia.

Somalia accused landlocked Ethiopia of attacking its sovereignty after Addis Ababa reached the agreement with Somaliland that gives long-sought access to the Red Sea.

Somaliland, a former British protectorate of about 4.5 million people, declared independence from Somalia in 1991, a move not recognized internationally and staunchly opposed by Mogadishu.

"The United States recognizes the sovereignty and territorial integrity of the Federal Republic of Somalia within its 1960 borders," State Department spokesman Matthew Miller told reporters.

"We join other partners in expressing our serious concern," he said, "about the resulting spike in tensions in the Horn of Africa."

"We urge all stakeholders to engage in diplomatic dialogue," he said.

Somaliland president Muse Bihi Abdi, who signed the deal with Ethiopian Prime Minister Abiy Ahmed, said that in return for providing sea access, Ethiopia would "formally recognize" Somaliland.

The Ethiopian government has not confirmed that it would recognize Somaliland. Somalia has withdrawn its ambassador from Addis Ababa and vowed to defend its sovereignty.

But Somalia has been in near constant chaos the past three decades. Somaliland has been seen as offering an oasis of stability, although it has failed to achieve international recognition.

Ethiopia was cut off from the coast after Eritrea seceded and declared independence in 1993 following a three-decade war, forcing Africa's second-most populous nation to channel commerce through an expensive arrangement with Djibouti.