"Secretary of Defense James N. Mattis embarks Sunday, September 16 on a trip to Skopje, Macedonia to show US support for Macedonia during NATO accession and continued US commitment to peace and security in the region," the advisory said.
Mattis had previously said that he would visit Macedonia ahead of an upcoming referendum on the change of the country’s name on September 30, while expressing concern about possible Russian interference in the process.
READ MORE: Concerned About Russian ‘Mischief,' US Defense Secretary to Visit Macedonia
A number of Western leaders — including Angela Merkel, Sebastian Kurz and Theresa May — have recently visited Macedonia in an effort to persuade Macedonians to participate in the referendum.
Macedonians have engaged a campaign of mass boycott, calling the referendum an attempt at genocide that seeks to legitimize the treasonous actions of the US-installed government of Zoran Zaev to undo the Macedonian nation-state and shift the responsibility onto them.
READ MORE: Macedonia on Edge Amid Fears of Manipulation in Looming EU, NATO Membership Vote
Greece has blocked Macedonia from entering NATO and the European Union despite a 1995 bilateral Interim Accord to allow Macedonia’s membership not under its name, but under the provisional reference "former Yugoslav Republic of Macedonia." Moreover, NATO has said the alliance was not bound by a 2011 International Court of Justice ruling that Greece has violated the Interim Accord.