The battle lines for a vote on Scottish independence are being drawn with a referendum deal to be agreed by the prime minister and first minister.
David Cameron and Alex Salmond will sign an agreement between the UK and Scottish governments in Edinburgh.
It will pave the way for the referendum in autumn 2014, with a single Yes/No question on Scotland leaving the UK.
The deal will also allow see the voter age lowered, allowing 16 and 17-year-olds to take part in the ballot.
The UK government, which has responsibility over constitutional issues, is expected to grant limited powers for the Scottish Parliament to hold a legal referendum, under a mechanism called Section 30.
Mr Salmond said the agreement would mean a referendum “made in Scotland”, while the prime minister said keeping the United Kingdom together was his number one priority.
The Electoral Commission watchdog will play a key role advising on the wording of the question and other issues such as campaign finance.
A possible second question on greater powers has been dropped, while the Scottish government looks to have secured its preferred date.
Speaking ahead of meeting, Mr Salmond said: “The agreement I expect to reach with the prime minister is one which ensures that not only is the referendum made in Scotland, but that the fundamental right of the people of Scotland to choose their own future is respected by all.
“The agreement will see Scotland take an important step toward independence, and the means to create a fairer and more prosperous Scotland. I look forward to working positively for a ‘yes’ vote in 2014.”
The SNP secured a mandate to hold the referendum after winning an unprecedented majority in the Scottish Parliament election last year.
In a speech later, Mr Cameron will say: “This marks the beginning of an important chapter in Scotland’s story and allows the real debate to begin.
“It paves the way so that the biggest question of all can be settled: a separate Scotland or a United Kingdom? I will be making a very positive argument for our United Kingdom.
“It is now up to the people of Scotland to make that historic decision.”
The prime minister will also say: “The very future of Scotland depends on their verdict. It is that important.
“This agreement delivers the people’s referendum.”
The deal was negotiated between Scottish Secretary Michael Moore and Scotland’s ddeputy ffirst mminister, Nicola Sturgeon.
BBC Scotland political editor Brian Taylor said: “The real significance of today’s agreement is this – the two leaders agree the rules for the referendum and, by implication, agree to respect and accept the outcome. Whatever it is.”