Prime Minister David Cameron has said Scotland could get enhanced powers if voters reject independence in a straightforward yes-no ballot.
During a visit to South Queensferry, near the Forth Bridge, he said it would be inappropriate to allow a second question in the referendum on enhanced powers, known as "devo-max".
"There's a simple question here that we need to settle, which is does Scotland want to stay in the United Kingdom? I think she does," he said.
"We have to settle that question, the question that arises because there's an SNP majority in Scotland.
"We have to settle that question before going on and asking, quite legitimately, is there more we can do to improve the devolved settlement? Are there other powers that can be devolved? How can we make the United Kingdom work better?
"I believe in devolution. I don't just mean devolution in terms of power, I mean devolution in terms of giving people greater power over their own lives."
Mr Cameron also took a tour of the Quaker Oats factory in Cupar, Fife, on the day that it announced a £14.4 million investment and 30 new jobs at the site.
He repeated his insistence that businesses regularly question him about investment in Scotland amid the "uncertainty about Scotland's future" created by the independence referendum.
Speaking after Mr Cameron's visit, Richard Evans, the UK president of Quaker's parent company PepsiCo, said today's announcement "is evidence that we are continuing to invest" and suggested there could be more investment in the next 12 months.
Mr Cameron said: "I am a patriot for the whole United Kingdom.
"I've got Cameron blood, and I've got Llewellyn blood. I was born and brought up in England, I'm proud to be English but also proud to be British and I think many people in the UK absolutely feel that you can have all of these identities together, and that is the strength of the UK."
When asked whether a Scottish patriot would prefer the seat of government in their home nation or in another nation, Mr Cameron said: "I think what the Scottish patriot wants is to have decisions made locally in Scotland, for Scotland, but also be part of a larger entity - the United Kingdom."
Mr Cameron added: "That (the UK) gives you enormous influence and reach that makes all of us, not just Scots but English, Northern Irish and Welsh people, stronger, richer, better protected and a fairer country.
"It's all of those things together. You can be a proud Scottish patriot and a proud inhabitant of the United Kingdom."
Mr Cameron said it is "very good news that PepsiCo has made this investment decision", describing it as "a vote of confidence" for the workforce and produce.
He added: "There's no doubt in my mind that if there's uncertainty about Scotland's future, there will be companies and business organisations that will start to ask questions about where to invest, and I hear that very directly as Prime Minister as companies raise that issue with me."
Mr Evans, president of PepsiCo UK & Ireland, said the political environment of a country is a consideration when it makes investment decisions.
He said: "Control of the public purse gives us an environment where we feel safe to invest, where we can continue to invest into the UK, and that's what you see today with the investment that we have made over the last year, and I've got no doubt that there will be more investment coming in the next 12 months if we continue to grow as we do."
He added: "I think in terms of the Scottish question as it stands right now, there are no specifics that any business is going to be able to comment on."
When asked whether lack of specifics affects PepsiCo's investment decisions, he said: "The evidence of our investment is here right now, so rather than answering with hypotheticals, right now we've put £14.4 million into a site that we have put roughly £51 million into over the last decade, and we're creating 30 new jobs.
"I think that is evidence that we are continuing to invest in the business."