By Oana Lungescu
BBC News, Brussels
The Slovenes and Croats argue over the bay of Piran
Slovenia has at the last minute cleared the way for its neighbour Croatia to join Nato later this week.
Croatia's accession had been threatened by a Slovene nationalist group, angry over a continuing border dispute.
The group had hoped to force a referendum on whether Slovenia should block Croatia's entry - but failed to gather enough signatures.
Croatia, along with Albania, is now set to join the alliance at a summit in Strasbourg later this week.
The Slovene problem has been resolved, a senior Nato diplomat announced with obvious relief.
Nato will mark its 60th birthday at the Strasbourg summit with a symbolic expansion into a region which which only a decade ago was at war.
But tensions between Croatia and Slovenia remain.
Slovenia continues to block its neighbour's accession to the European Union because of the border dispute that has simmered since both countries declared independence from Yugoslavia 18 years ago.
Meanwhile Macedonia, another former Yugoslav republic which had also hoped to join Nato this week, remains locked in an arcane row with Greece over its name.
Athens says it implies territorial claims over Greece's northern province, also called Macedonia, leading to the country's formal name of the Former Yugoslav Republic of Macedonia.
If the main point of admitting Balkan countries into Nato and the EU is to persuade them to leave their nationalist past behind, it appears it is not entirely working.