North Macedonia joined the Partnership for Peace in 1995, and commenced its Membership Action Plan in 1999, at the same time as Albania. At the 2008 Bucharest summit, Greece blocked a proposed invitation because it believed that its neighbor's constitutional name implies territorial aspirations toward its own region of Greek Macedonia. NATO nations agreed that the country would receive an invitation upon resolution of the Macedonia naming dispute. Macedonia sued Greece at the International Court of Justice (ICJ) over their veto of Macedonia's NATO membership. Macedonia was part of the Vilnius Group, and had formed the Adriatic Charter with Croatia and Albania in 2003 to better coordinate NATO accession.