NATO Secretary General Anders Fogh Rasmussen has welcomed the news that Britain will remain a united country following Scotland's referendum rejecting independence.
"The United Kingdom is a founding member of NATO and I am confident that the United Kingdom will continue to play a leading role to keep our Alliance strong," Rasmussen said in a statement.
"I welcome Prime Minister Cameron's statement that the United Kingdom will go forward as a united country."
The United States and other allies had expressed concern that breaking up Britain, whose nuclear missile force is based in Scotland, could weaken an important member of NATO.
Scotland needs to unite now the referendum result is in, the leader of the victorious Better Together campaign told Good Morning Britain.
Alistair Darling directly addressed fears Scotland would split from the 307-year-old union when the results of YouGov poll showed 51% intended to vote Yes, but said he "was very clear...that we were going to win".
David Cameron's decision to devolve voting powers on English issues to English MPs alone could cause a major issue for the Labour Party, reports ITV News Political Editor Tom Bradby.
In the event that Labour wins the next election with a slim majority, it may rely on MPs in Scotland that would then be ineligible to vote on English matters such as a budget.
That may mean major bills such as the Budget could be at risk of failure without cross-party support.
Northern Ireland First Minister Peter Robinson has said he is "delighted" Scotland has chosen to remain in the United Kingdom.
The final vote in the Scottish referendum from the Highlands is a No vote.
The Yes campaign had already conceded they had lost but the last vote was in favour of staying united by 53% to 47%.
Better Together leader Alistair Darling praised the "influential" role of Gordon Brown in the No campaign, saying the speech given by the former Prime Minister was "vintage".
Darling told Good Morning Britain:
David Cameron's plans to have English devolution presided over by William Hague and a committee are "dangerous", Nigel Farage has told Good Morning Britain.
The Ukip leader said the Prime Minister was "panicking" by saying, "I'm going to put William Hague in charge of a committee and after a few weeks we're going to find a solution to run in a parallel timetable with more Scottish devolution."
Businesses across the UK are breathing a "collective sigh of relief" following the announcement that Scotland will remain part of the United Kingdom, the Confederation of British Industries has said.
The UK's FTSE 100 index rose by 0.7 percent early on Friday, with Scottish-based stocks such as Royal Bank of Scotland and energy firm SSE among the top-performers, rising by 3.2 and 3.3 percent respectively.
CBI director-general John Cridland said: "Business has always believed that the union is best for creating jobs, raising growth and improving living standards, and welcomes that the people of Scotland want to play an integral role in this internationally successful partnership.
He added that as further devolution is discussed, "it is important that it does not undermine the strength of the single internal market and it is in the best interests of citizens living in England, Wales and Northern Ireland, as well as those in Scotland".
The head of the Local Government Association, which represents councils in England and Wales, has said "the devolution genie is out of the bottle" following the Scottish referendum.
David Sparks said any new powers that Scotland receives "must be given to local areas in England and Wales", adding: "The appetite for devolution does not stop at the border and the rest of the UK will not be content to settle for the status quo."
The LGA called for an urgent meeting of a Constitutional Convention and called on the Government to set out a timetable for devolution across England, with a pledge for immediate new powers to areas which are ready for them.