Prime Minister David Cameron and Scottish First Minister Alex Salmond are to meet in Edinburgh on Monday to finalise arrangements for a historic referendum on Scottish independence.
If agreed, the plan envisages a vote north of the border in autumn 2014.
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 many Scottish 16-year-olds to vote in the referendum.
Downing Street declined to confirm reports of the timing and location of the meeting, saying only that Mr Cameron will meet the First Minister "shortly".
In common with the leaders of the other major British parties, Mr Cameron has pledged to campaign hard against Scottish independence, which is the key political goal of Mr Salmond's Scottish National Party.
The announcement came after "substantial progress" was made during discussions between the Westminster and Holyrood governments over how and when the referendum should be held.
Deputy First Minister Nicola Sturgeon and Scottish Secretary Michael Moore met for talks on the referendum issue on Tuesday afternoon. Discussions included the use of a Section 30 order which would transfer power to Holyrood to legislate on the referendum.
A joint statement issued by the Scottish Government and the Scotland Office after the meeting said: "Further substantial progress towards agreement was reached this afternoon between the Deputy First Minister Nicola Sturgeon and the Secretary of State Michael Moore.
"Officials have now been tasked with doing some further work on the final detail of the agreement. We are however on track for the full agreement, including the terms of a section 30 order, to be presented to the First Minister and the Prime Minister over the next few days."
Shadow Scotland secretary Margaret Curran said: "It is right that the people of Scotland are given a clear choice. Now we need to see the political wrangling replaced by real debate about the case for maintaining the United Kingdom. North and south of the border, a One Nation Labour Party will play its part and make the case that we are better binding together to tackle the challenges we face, instead of going our separate ways."