"Pleased to announce the United States deposited its ratification of North Macedonia's NATO Accession Protocol", Pompeo tweeted late Sunday.
In October, the Senate approved a decision by the US government to support Macedonia's entry into the alliance by a bipartisan vote of 91 to two. Only Republican Senators Rand Paul and Mike Lee voted against.
Macedonia has been participating in the NATO Membership Action Plan (MAP) since 1999. MAP provides advice and assistance tailored to the individual needs of countries wishing to join the alliance.
The country was invited to join the bloc at the Bucharest summit in 2008 as long as it reached consensus with Greece in their years-long naming dispute.
The dispute was resolved in June 2018 when the country renamed itself North Macedonia to appease Greece and pave the way for EU and NATO membership.
In early October, Pompeo met with Macedonia's President Pendarovski to discuss the country's accession to NATO.