David Cameron has promised to campaign against Scottish independence with "everything we've got" as negotiations over a referendum enter their final stages.
The Prime Minister will meet Scottish First Minister Alex Salmond on Monday to finalise arrangements for the referendum expected in autumn 2014.
In his speech to the Conservative Party conference, Mr Cameron asked: "What could matter more than saving our United Kingdom?"
The referendum ballot paper is expected to have a single Yes/No question on whether Scotland should leave the United Kingdom. It is also expected that the agreement will make provisions for 16-year-olds in Scotland to vote in the referendum.
Mr Cameron told activists in Birmingham that the Olympics had highlighted the depth of feeling for the United Kingdom.
"Whether our athletes were English, Scottish, Welsh or from Northern Ireland, they draped themselves in one flag. Now, there's one person who didn't like that and he's called Alex Salmond. I'm going to see him on Monday to sort out that referendum on independence by the end of 2014.
"There are many things I want this coalition Government to do but what could matter more than saving our United Kingdom? Let's say it: we're better together and we'll rise together - and let us fight that referendum with everything we've got."
Mr Salmond, speaking in Edinburgh, insisted there is still work to be done to finalise the decision on the staging of the referendum.
Scottish Secretary Michael Moore and Deputy First Minister Nicola Sturgeon - leading negotiations for the two governments - still have work to do, he said.
"Great progress has been made and I'm certainly hoping and optimistic that a deal can be done next week," he added. "But a deal ain't done until it's finalised. There are a number of issues that are still to be resolved. I hope they can be resolved - that's the expectation."