EDINBURGH (Reuters) - Scotland will hold its independence referendum on Sept 18, 2014, First Minister Alex Salmond said on March 21, starting the countdown to a vote he hopes will take his nation of 5 million out of the United Kingdom.

Mr Salmond's pro-independence Scottish National Party (SNP) won a majority in the Scottish parliament in the May 2011 elections, giving the charismatic politician what he has called a"once-in-a-generation" chance to break ties with London.

The SNP faces an uphill battle to win the referendum, whose terms were agreed with the British government last October.

Opinion polls put support for independence at about 30 per cent of the electorate in Scotland while about 50 per cent favour the status quo.

The SNP complains that the British parliament, where members representing Scotland are a small minority because England has a much bigger population of 53 million, does not have the particular interests of the Scottish people at heart.

"A yes vote means a future where we can be certain, 100 per cent certain, that the people of Scotland will get the government that they vote for," Mr Salmond told the Scottish parliament in a speech announcing the date of the referendum.

"The choice becomes clearer with each passing day - the opportunity to use our vast resources and talent to build a better country, or to continue with a Westminster system that
simply isn't working for Scotland."

The SNP argues that North Sea Oil revenues combined with the local farming, fishing and whisky industries would enable an independent Scotland to prosper.

But other parties in Edinburgh and the London government say both Scotland and the rest of the United Kingdom would lose out.

Critics of the SNP say oil reserves are dwindling and Scotland would lose the disproportionately generous share of taxpayer money raised across Britain that it currently receives.

Scottish secession would pose serious challenges to the remainder of the United Kingdom, such as what to do about its Trident nuclear submarine fleet which is based in Scotland.

There would also be big uncertainties for Scotland itself, such as whether it would be allowed to remain part of the European Union or whether it would have to negotiate re-entry.

The broad terms of the referendum were agreed by Mr Salmond and British Prime Minister David Cameron last October.

Voters will be asked a single question: "Should Scotland be an independent country?"