- Leaders of the three main UK parties give Scotland a joint promise of extra powers
- Voters will go to the polls Thursday to decide on independence for Scotland
- Prime Minister David Cameron begs Scotland to stay, says it's a "once-and-for-all decision"
- Pro-independence chief Alex Salmond says Scottish people want their future in their hands
The three main UK party leaders gave a joint promise Tuesday that Scotland will get extra powers if it opts to stay part of the United Kingdom in a landmark vote in two days' time.
Opinion polls have put the pro-independence and pro-union camps neck-and-neck in the run-up to Thursday's referendum.
With the survival of the 300-year-old union of England, Scotland and Wales as Great Britain on a knife-edge, UK Prime Minister David Cameron of the Conservatives, coalition partner Nick Clegg of the Liberal Democrats and Labour leader Ed Miliband have joined forces to beg Scotland to stay.
In a pledge published on the front page of Scotland's Daily Record newspaper, the three leaders say that if Scotland's voters reject independence, work to devolve "extensive new powers" from the central government in Westminster will start Friday.
The issue of spending on social welfare and health care, through the National Health Service, has been central to the pro-independence campaign. Questions over the economy and taxation have also been key.
In their promise, the leaders say "we can state categorically that the final say on how much is spent on the NHS will be a matter for the Scottish Parliament."
They conclude, "People want to see change. A No vote will deliver faster, safer and better change than separation."
With a huge turnout expected for the referendum, both sides are desperate to win over the undecided voters who could hold the future of the United Kingdom in their hands.
In a speech Monday in Aberdeen, Scotland, Cameron made an emotional plea for Scotland not to "end the United Kingdom as we know it" and warned that there was no turning back if voters decide on independence.
"This is a decision that could break up our family of nations, and rip Scotland from the rest of the UK," he said.
"And we must be very clear. There's no going back from this. No rerun. This is a once-and-for-all decision.
"If Scotland votes yes, the UK will split, and we will go our separate ways forever."
Cameron said he spoke for millions of people across the United Kingdom -- including in Scotland -- who would be "heartbroken" to see Scotland leave, and he warned that it would be a "painful divorce."
The "Yes Scotland" campaign, led by Scotland's First Minister Alex Salmond, says that only by voting for independence can Scotland be sure that it will have full control of its own taxation and spending.
Salmond, speaking in Edinburgh on Monday, called the vote a "once-in-a-lifetime opportunity" for Scotland.
"Nobody goes back" from independence, he said. "The evidence is that more and more people in Scotland are wanting to put Scotland's future into Scotland's hands."
The yes/no referendum question will ask voters, "Should Scotland be an independent country?"
White House: We want a strong, robust UK
White House spokesman Josh Earnest weighed into the debate Monday, echoing remarks previously made by U.S. President Barack Obama.
"This is a decision for the people of Scotland to make," he said. "We certainly respect the right of individual Scots to make a decision about the -- along these lines.
"But, you know, as the President himself said, we have an interest in seeing the United Kingdom remain strong, robust, united and an effective partner."
Many unanswered questions revolve around defense if Scotland votes for independence. The Scottish National Party, headed by Salmond, has said it wants to remove the UK nuclear submarine fleet from Scottish waters as soon as possible.
'A fool's errand'
The debate has polarized opinion in the business world, as well as in political circles.
The Financial Times published a full-page editorial last week headlined, "The case for union is overwhelming. The path of separation is a fool's errand."
Speaking to CNN's Christiane Amanpour this week, editor Lionel Barber said, "We really believe that it would be very dangerous and highly risky in terms of economics. ... We believe that the 'Yes' campaign has not answered important questions -- notably: What will the currency be? We don't know."
The three main parties in Westminster have said that an independent Scotland would not be able to keep the pound. There are also unanswered questions about tax increases and the fiscal implications of independence, Barber said.
While the newspaper does not deny that Scotland has the right to choose independence, he said, "We are just pointing to the dangers of uncertainty, the price of uncertainty, which will affect ordinary people."
Salmond, who met with business leaders in Edinburgh, said the "impressive array" of business leaders who back the independence campaign "is a very strong point in the 'Yes' campaign."
"These are the people looking forward to the realization that Scotland can have a more prosperous economy but also wants a more just society. And their voice and that combination of things is something that will carry a good deal of weight off the ballot sheet."