The EU on Tuesday welcomed a treaty on "friendship, good neighborliness and cooperation" signed between Bulgaria and Macedonia.
"This agreement demonstrates the determination of both sides to overcome bilateral issues and is an inspiration for the whole region," EU foreign policy chief Federica Mogherini and EU Enlargement Commissioner Johannes Hahn said in a statement.
It said the deal was a "positive" step forward in good neighborly relations and boosts the EU perspective of Macedonia in the interest of its citizens.
As an EU candidate country since 2005, Macedonia has faced obstacles from Bulgaria over historical, linguistic and religious issues.
Sofia still does not recognize the Macedonian language and until recently was opposed to Skopje's efforts to become a NATO member.