LONDON (AP) — Britain's prime minister on Monday outlined who will be allowed to vote in a referendum on whether Britain should remain in the European Union, opting to exclude most voters from the other 27 EU nations living in the U.K.

Prime Minister David Cameron announced the parameters ahead of introducing legislation Thursday in Parliament to organize the ballot. No date has been set for it yet but Cameron is committed to holding the referendum by 2017.

His plans include a tour of European capitals to press his case that the EU needs to be reformed, hoping that the upcoming vote in Britain will convince those on the continent that Britain is determined to enact change.

Cameron plans to travel to Denmark, the Netherlands, France, Poland and Germany this week as part of his efforts to talk with all of the leaders of the EU member states before the European Council late next month.

Under the referendum measure, the vote will be open to those allowed to vote in British elections rather than rules used for European Parliament or local elections.

Cameron said U.K.-resident citizens of four other EU members — Ireland, Commonwealth members Cyprus and Malta, and the U.K.'s own territory of Gibraltar — will be eligible to vote, while citizens from 24 other EU nations will not.

This means more than half of eligible voters among the 2.8 million non-British EU citizens living in the United Kingdom will be denied a ballot in the referendum.

Uniquely, Cameron plans to permit eligible voters in Gibraltar, the British territory on the Mediterranean Sea, to take part. That decision could aid the pro-EU side, because Gibraltar's 30,000 residents broadly see EU membership as essential to thwarting Spain's ambitions of claiming the 2.6-square-mile (6.8-square-kilometer) territory.

The chief minister of Gibraltar, Fabian Picardo, praised Cameron for being "true to his word" on giving the territory's residents a chance to vote.

"As a British part of the EU, our voice will be heard as part of the franchise for this seminal exercise in democracy," he said.