EDINBURGH - Scots began voting in an independence referendum on Thursday that will decide the fate of the United Kingdom, after opinion polls showed hundreds of thousands of them were still agonizing over whether to stay with the 307-year union or back secession.In the final hours before polling stations opened, leaders of both sides urged Scots to seize the reins of history in a vote that has divided families, friends and lovers but also electrified this country of 5.3 million.From the remote Scottish islands of the Atlantic to the toughest city estates of Glasgow, voters are being asked to answer "Yes" or "No" to the question: "Should Scotland be an independent country?""This is an historic day for Scotland. I've waited all my life for this. It's time to break with England. 'Yes' to independence," said a businessman who gave his name as Ron and was the first person to vote at Edinburgh's Waverley Court.As he spoke, a couple of workers hurrying by in the morning mist and drizzle shouted "Vote No!"Five surveys - from pollsters YouGov, Panelbase, Survation, Opinium and ICM - showed support for independence at 48 percent, compared with 52 percent for the union.An Ipsos MORI poll showed it even closer at 49 percent to 51 percent, while a second Survation poll, conducted by phone, showed unionists at 53 percent and separatists at 47 percent.The surveys also showed as many as 600,000 voters remained undecided, making the vote far too close to call. Polling stations close at 2100 GMT and a result is expected early on Friday."This is our opportunity of a lifetime and we must seize it with both hands," Alex Salmond, Scotland's 59-year-old nationalist leader, told hundreds of supporters who waved the white on blue Scottish flag and chanted "Yes we can.""Scotland's future must be in Scotland's hands," Salmond said in Perth, a city in eastern Scotland 460 miles (740 km) north of London.The independence movement says Scots should be able to choose their own leaders and make their own decisions rather than be ruled from London. Supporters of the union say Scotland is more prosperous and secure as part of the United Kingdom and the ties that bind them are too tight to be undone.But with a mix of shrewd calculation and nationalist passion, Salmond has hauled the "Yes" campaign from far behind to within a few percentage points of winning his dream of an independent Scotland.Facing the biggest internal threat to the United Kingdom since Ireland broke away nearly a century ago, Britain's establishment - from Prime Minister David Cameron to corporate bigwigs and the princes of pop culture - have united in a last-ditch effort to convince Scots that the United Kingdom is "Better Together".Cameron's job could be on the line if Scotland breaks away, but the 47-year-old prime minister has conceded that his privileged English background and Conservative politics mean he is not the best person to win over Scots.That has left the leadership of the unionist case in the hands of the opposition Labour party, winner of 41 Scottish seats in the 2010 British election and the only party with the local support capable of checking the secessionist Scottish National Party.Former Labour Prime Minister Gordon Brown, a Scot who has in recent days led the battle cry for the union, on Wednesday warned Scots in Glasgow, Scotland's biggest city and a crucial battleground, that Salmond was "leading us into a trap"."Have confidence, stand up and be counted tomorrow," Brown thundered, fists clenched, to applause and cheers from unionist supporters. "Say to your friends, for reasons of solidarity, sharing, pride in Scotland, the only answer is vote 'No'."A UNITED KINGDOM?In the event of a vote for independence, Britain and Scotland would face 18 months of talks on how to carve up North Sea oil and what to do about European Union membership and Britain's main nuclear submarine base.Scotland says it will use the pound after independence, but London has ruled out a formal currency union, while Britain will have to decide what to do about the nuclear submarine base on the Clyde, which the nationalists want to evict.The prospect of breaking up the United Kingdom, the world's sixth-largest economy and a veto-wielding permanent member of the United Nations Security Council, has prompted citizens and allies alike to ponder what would be left, while the financiers of the City of London have warned of market turmoil.Salmond has accused London of orchestrating a campaign by business leaders aimed at spooking Scots after businesses from oil giant BP to financial services group Standard Life cautioned about the risks of independence.The United States has made clear it wants the United Kingdom, its main ally in Europe, to remain together."The UK is an extraordinary partner for America and a force for good in an unstable world. I hope it remains strong, robust and united," .. President Barack Obama said.To blunt Salmond's argument for breaking away, Britain's rulers promised to guarantee Scotland high levels of state funding and grant Scots greater control over finances.British leaders accept that even if Scotland votes to keep the union, the United Kingdom's structure will have to change, as granting further powers to Scotland will provoke calls for a less centralised state from voters in England, Wales and Northern Ireland.TOO CLOSE TO CALLFive of the polls showed nationalists had gained ground, but supporters of the union were slightly ahead in all seven polls as some currency traders in London prepared to stay up all night on Thursday to buy or sell sterling on the results of the vote.US Treasury Secretary Jack Lew said there were potentially significant economic ramifications from the vote and that a strong United Kingdom was important.British finance minister George Osborne has cancelled a trip to a G20 meeting of finance ministers in Australia while Bank of England Governor Mark Carney will be in London for the result of the Scottish vote.One poll, from Panelbase, showed support for independence had slipped to 48 percent from 49 percent, while YouGov, which had the biggest sample of the campaign, had support for independence unchanged at 48 percent.Electoral officials said the result of the vote is expected by breakfast time on Friday morning, but partial results will give an indication of the trend after the count of major cities such as Glasgow are declared around 0400 GMT. With more than 486,000 voters, Glasgow is crucial, and the way its traditional Labour supporters go could be decisive.Edinburgh and Aberdeen, which with Glasgow make up nearly a quarter of the vote, are also expected around about that time. Helicopters will fly from specially lit landing sites from remote islands to deliver ballot boxes to regional counting centers.Police played down the prospect of violence, and the leaders of both campaigns have said they will accept the will of the people no matter what the result and seek to work for Scotland.In such a tight contest, the "undecideds'" final decisions could still swing the vote.On the night before the ballot, Edinburgh voter Karen Wood told Reuters she had still not made up her mind."At the moment it is just the uncertainty of what Scotland has got in store for everyone. It's worrying. It is just such a huge decision to make."The second voter out of the Waverley Court polling station said he wanted change for Scotland."It's brilliant, it's very exciting," 51-year-old Jack McGinn said. "I'm a homeless veteran. How can that be in 2014? I voted for independence."