David Cameron has spoken to European leaders and agreed to push ahead with Russian sanctions by the end of the week, his spokesman has confirmed.
- ITV News' Political Editor Tom Bradby reports:
The Prime Minister gave a strangely anti-politics speech. In a way, he was effectively saying "look at all the things we've done together as people: standing in the trenches, defeating fascism and all the rest of it."
He has been criticised throughout for not showing enough emotion. I think everyone this week has woken up to the fact that independence is a real possibility, including the Prime Minister, and he is a bit desperate.
I think part of that desperation is about emotion. I don't doubt that he personally cares a lot about the union and would be devastated if it split up.
The Prime Minister has said he cares "far more about his country than his party", as he visits Scotland in a bid to increase support for the No campaign ahead of the referendum.
During a visit to the Scottish Widows offices in Edinburgh, David Cameron said: "I care hugely about this extraordinary country, this United Kingdom that we've built together. I would be heartbroken if this family of nations that we've put together was torn apart."
He added it was important to "talk about what we care about and how we feel about this amazing country, the United Kingdom, that we've built together."
The Prime Minister has declined to give a timetable for the removal of the Trident nuclear weapons system, which is based in Scotland, defending what he called the "ultimate insurance policy".
He said that the UK was safer because of its strong armed forces, and that he would not leave Britain "subject to blackmail by other countries that have nuclear weapons".
The Prime Minister has said there is "very wide agreement" between the pro-union parties on the issue of devolution.
He said there was "very clear political will among the parties and that's as close to a guarantee [of devolution] as you can get".
The Prime Minister has said: "If Scotland votes for separation that vote has to be respected by the rest of the UK, and as prime minister of the UK I would have to make that happen, though it would be heartbreaking."
The Prime Minister has told voters in Scotland: "We should be clear that if you leave the UK, you leave the currency, you leave the pound."
He also said he thought the former prime minister Gordon Brown was "spot on" when he unveiled a timetable for devolution.
"Not often you see me and Gordon in absolute agreement," he added.
David Cameron has urged Scots not to vote for independence just to punish the "effing Tories".
Speaking in Edinburgh, the Prime Minister said: "Because it is an election people think it's like a general election.
"If you are fed up with the effing Tories give them a kick.
"This is not a decision about the next five years, but the next century."
David Cameron has pleaded with Scotland's voters not to "rip apart" the union as he issued a warning that independence is a "leap into the dark" from which there is no going back.
In an article for the Daily Mail, the Prime Minister writes, "Our message to the Scottish people will be simple: We want you to stay."
"Together, the United Kingdom embodies the values the world looks on with awe and envy," he wrote, highlighting achievements such as the NHS and the state pension system.
"The United Kingdom is a precious and special country. That is what is at stake. So let no-one in Scotland be in any doubt: we desperately want you to stay; we do not want this family of nations to be ripped apart."