Gibraltar was made a provisional member of UEFA on Friday by European soccer's governing body.
The decision was made despite FIFA, which runs the world game, rejecting Gibraltar's application for member status on Wednesday.
UEFA said it "had no choice" but to admit the Gibraltar Football Association after a ruling by world sport's highest tribunal. The Court of Arbitration for Sport ruled this month in favor of Gibraltar's application.
Spain is expected to seek support in opposing full membership, which would allow Gibraltar to participate in competitions and can only be granted by UEFA's Congress, which meets Jan. 26-27 in Duesseldorf, Germany.
Full membership would allow Gibraltar to take part in next season's UEFA Cup and qualifiers for the 2012 European Championship, reports AP.
Gibraltar, on Spain's southernmost tip, has been a frequent source of tension between Britain and Spain, which claims sovereignty over the territory.
Spain said UEFA's own statutes exclude Gibraltar, because the British colony does not have individual representation at the United Nations.
In 1999, Spain succeeded in having UEFA change its rules so that new members have to be U.N.-recognized states. However, Gibraltar's original application predates this change and the soccer association hopes to avoid exclusion.
Gibraltar's soccer team is more than 100 years old.
A rocky territory where the Mediterranean Sea meets the Atlantic Ocean, Gibraltar has a population of about 29,000 and sends teams of competitors to the Commonwealth Games. It does not have a recognized National Olympic Committee.