Alex Salmond has pressed David Cameron for a debate on Scottish independence in response to a new poll which suggests English politicians getting involved is more likely to make Scots vote Yes.
Over two-fifths (43%) of British people think English interventions in the debate will boost the chances of an independent Scotland, a You Gov poll for Sky News has found.
Nearly a third (31%) think English politicians should stay out of the debate, rising to 44% amongst people in Scotland.
Mr Salmond, Scotland First Minister and leader of the Scottish National Party, told Sky News: "I'm in favour, actually, of people getting involved.
"The Prime Minister, for example, I think he should get involved but I think he should debate.
"I don't think he should just come up to Scotland and get involved and go away again.
"Let's debate First Minister to Prime Minister. Let's get some real involvement and hopefully that will help people vote Yes."
Mr Salmond has also said he was surprised by US President Barack Obama's intervention in the independence debate last week, when he said he wants to ensure the UK remains "strong, robust and united".
He told the BBC's Andrew Marr show: "It was certainly surprising because the American government had made it very clear that they were staying studiously neutral in the democratic referendum that is taking place in Scotland.
"But of course David Cameron has been begging everybody internationally to say anything to help him in his travails at the present moment.
"He's right to be worried - we had the latest Yes poll at 46%.
"So perhaps on the Richter scale of presidential interventions this was quite mild.'It's a matter for the folks in Scotland' and he hopes that the UK will remain 'strong and united' as an ally.
"Well if Scotland becomes independent then America will have two allies in these islands, not just one."
Former SNP defence adviser Lieutenant-Colonel Stuart Crawford has claimed that the US would block or delay Scottish Nato membership if it insists on Trident submarines being quickly withdrawn.
"I have spoken to a source close to the White House who said if an independent Scotland were to demand the removal of Trident from the Clyde, Scotland's accession to Nato would either be blocked or delayed for a very long time," he told the Sunday Times.
But Mr Salmond said it "wouldn't be realistic" to keep nuclear weapons in an independent Scotland.
"If the rest of the UK wants to retain a nuclear capability then they can do so," he told Andrew Marr.
"I think they would be very unwise to do so, incidentally, but it wouldn't be realistic to have nuclear weapons stationed in Scotland after independence."
His comments come on the eve of the 100 day countdown to the independence referendum, which will give Scotland an opportunity "to address the economic and social challenges it faces", according to Mr Salmond.
"Tomorrow marks the start of that countdown to what will be one of the most exciting and historic days this nation has ever seen," he said.
Scottish Liberal Democrat leader Willie Rennie is calling on party activists and pro-union campaigners to make a positive case for a "stronger Scottish parliament which stays in the UK family" over the summer.
He said: "With 100 days until the referendum, Liberal Democrats have a golden opportunity to loudly state our case for home rule for Scotland in a federal United Kingdom.
Former Labour minister Lord John Reid has urged the pro-UK campaign to up its game amid concerns that a Yes vote is "possible".
"I wouldn't say that we have done everything right and, yes, we can always improve," he told BBC Sunday Politics Scotland.
When asked if the Yes campaign could win, he said: "I don't think it but it is always possible. In politics everything is possible.
"I think over the next 100 days there are three issues that will decide this. One is the economic and material advantages we have in the UK which is becoming more obvious. Second is the risks of separation, whether on pensions, Europe, the economy and others. Thirdly, the emotional argument which applies on both sides."
Lord Reid - who held a string of cabinet posts under Tony Blair including the Home Office, Defence, Health and the Scotland and Northern Ireland Offices - made his first major intervention for Better Together in a speech in Stirling yesterday.
His former cabinet colleague Alistair Darling is leading the Better Together campaign.
Mr Darling opened a Better Together campaign office in Edinburgh this afternoon, one of nine offices they are opening around Scotland to "step up the tempo of the campaign".
He said Lord Reid is "dead right" that campaigners must put their utmost effort into securing a No vote because "it's not over till it's over".
And Mr Darling accused Alex Salmond of "dodging debating with fellow Scots" in his relentless pursuit of a debate with the Prime Minister.
"I've got a vote in Scotland on September 18 and so does he - he should be debating with me and if he wants to avoid doing that people will judge him," he said.
Commenting on the Sky News poll, Mr Darling said: "The only people that have got a vote are people on the electoral roll in Scotland, but the views of people in other parts of the UK matter to all of us.
"I am heartened that so many people living outside Scotland want Scotland to stay."
He said discussions on Scotland's Nato membership would be "long, difficult and unnecessary" as Scotland could avoid the disruption by voting No.
He added: "Over the next 100 days we are moving into the final phases of the campaign, you will see increased activity and action the length and breadth of Scotland.
"So I am very confident that we will win this.
"I think in any referendum campaign, in any contest like this, it's not over till it's over.
"(Lord Reid) is dead right, everybody needs to do as much as they possibly can and more if we're going to get the result that we want in September.
"We are very confident that we have got momentum. The other side have given up on their economic arguments altogether while we have got stronger arguments of the head and heart which is why I think we will win."