MADRID: President Joe Biden supports a deal that will allow Finland and Sweden to join NATO and played a behind-the-scene role in the Nordic countries' negotiations with Turkey, a senior U.S. official said on Tuesday.

Turkey dropped its opposition to Finland and Sweden joining NATO in time for the alliance's annual summit in Madrid. The official, speaking to reporters on condition of anonymity, said Biden spoke to Turkish President Recep Tayyip Erdogan about NATO earlier on Tuesday at the request of the two nations.

Finland, Sweden back on path to NATO membership as Turkey drops veto

The official said the agreement will allow for an expansion of the 30-member alliance and mark "a significant sea change in the security posture."

Turkey did not insist that its demands for advanced American warplanes be included in the negotiations, the official said. Biden and Erdogan are expected to meet on the sidelines of the summit on Wednesday.