The parliament of Montenegro has ratified Finland and Sweden's accession to Nato.
The vote was announced in a tweet by the country's foreign minister Ranko Krivokapić on Friday.
However the issue still needs final approval from Montenegro's President Milo Đukanović.
Montenegro will be the 20th of Nato's 30 member states to ratify the Nordic countries' membership in the military alliance.
With 10 member states yet to approve Finland's membership in the alliance, some question marks remain.
While the US appears poised to overwhelmingly vote in favour of Finland and Sweden joining Nato, Rand Paul, a Republican senator from Kentucky is delaying the vote. His primary gripe is with Nato's Article 5, which ensures collective security to all members. He argues that any US action must require congressional approval, regardless of what the treaty stipulates.
Other concerns have arisen with Finland's Nato bid as politicians appear to use ratification as a bargaining chip. Besides Turkey's mercurial temperament on Finland and Sweden joining the alliance, issues with another member of the alliance popped up this week.
The governor of Italy's Friuli-Venezia Giulia region, Massimiliano Fedriga, asked his country's parliament to suspend the ratification of Finland's Nato membership on Wednesday. His justification was due to recently-announced plans by Finnish marine and energy equipment firm Wärtsilä to stop production at its facility in Trieste, Italy. Despite the governor's rhetoric, the Finnish economic affairs minister Mika Lintilä was unfazed and said he didn't "consider it a serious situation".