President Donald Trump on April 29 officially sent to the Senate for ratification the protocol for the Republic of North Macedonia to accede to NATO.

Macedonia’s accession to NATO will strengthen the alliance, contribute to regional stability in the western Balkans, and send a strong message to pernicious actors—such as Russia—that they do not have a veto right over the decision of the sovereign member states of NATO.

The protocol was signed by all 29 NATO members on Feb. 6 in Brussels. Former Sen. Kay Bailey Hutchison, permanent representative of the United States to NATO, signed the protocol on behalf of the U.S., and Macedonia since then has taken part in NATO activities as an invitee.

Once the protocol is ratified by all the legislatures of all 29 member states, then Macedonia will join the alliance as its 30th member state.

Macedonia’s accession to NATO will be a milestone for the alliance, the end of a decades-long dispute with Greece over its northern neighbor’s official name, and the successful culmination of U.S. leadership supporting the nation’s NATO aspirations.

That name dispute dates to the dissolution of Yugoslavia in 1991, when Macedonia became an independent state under its new constitutional name, Republic of Macedonia.

Greece quickly protested on the baseless grounds that the name Macedonia, which is the same as that of Greece’s northern province, implied regional territorial claims by the new nation.

In 1993, Macedonia joined the United Nations under the provisional name “the former Yugoslav Republic of Macedonia.” In 1995, Macedonia and Greece agreed to a U.N.-brokered interim accord, in which Athens agreed not to block Macedonia’s integration into international organizations, such as NATO, as long as it called itself “the former Yugoslav Republic of Macedonia” until both sides agreed on a mutually acceptable name.

Macedonia joined NATO’s Partnership for Peace in 1995 and received a membership action plan in 1999. Upon completing the plan in 2008—meaning it had met all requirements for joining the alliance—Macedonia anticipated an invitation to join that year at the NATO summit in Bucharest, Romania.

At the last minute, Greece unilaterally vetoed Macedonia’s accession over the name issue, a position that the Greek government stuck to until last year.

Last June 12, the two nations signed the Prespa Agreement, in which the Republic of Macedonia agreed to change its official name to the Republic of North Macedonia. In exchange, Greece dropped its opposition to the country’s accession to NATO and agreed to ratify “any of the Second Party’s accession agreement to International Organizations, of which the First Party is a member.”

On Jan. 11, Macedonia’s parliament passed an amendment to the constitution to change the formal name of the nation to Republic of North Macedonia. Two weeks later, on Jan. 25, the Greek parliament ratified the Prespa Agreement.

In Macedonia, the decision to change the nation’s official name was and remains controversial. Some Macedonians think the agreement does not do enough to preserve their unique national, cultural, and linguistic identity.

It’s in America’s interest that there be political stability in Macedonia and the western Balkans. The U.S should continue to keep in mind the concerns some Macedonians have over the name agreement and work to help ensure they are being addressed.

The U.S. has long led the way on Macedonia’s inclusion in NATO and for the alliance’s open-door policy. That open-door policy for qualified countries has contributed greatly to transatlantic security since the first round of enlargement in 1952 and helped to ensure the alliance’s central place as the prime guarantor of security in Europe.

NATO has also been a crucial driver of modernization and reform in candidate countries, has promoted stability and peace in Europe, and has made it easier for the alliance to coalesce around collective defense.

NATO has done more than any other organization, including the European Union, to promote democracy, stability, and security in the Euro-Atlantic region. That was accomplished by enticing countries to become a part of the club.

While it may be tempting to view Macedonia’s likely accession to NATO as a closing ceremony for enlargement, that would be a substantial mistake. It’s in America’s interest that NATO’s door remains open to other deserving European countries.