Heading to Scotland for talks on an independence referendum, British Prime Minister David Cameron said Thursday that he would fight "head, heart and soul" to prevent the breakup of the United Kingdom.

Cameron was scheduled to hold his first meeting on the issue with Scotland's leader Alex Salmond, whose separatist party has long campaigned for the nation to leave its neighbors behind for the first time in more than 300 years.

Salmond is seeking to hold an independence referendum in September 2014, hoping that a separation from London would be completed with a May 2016 election for the Scottish Parliament.

However, with opinion polls showing that only about a third of Scots currently favor splitting the nation, Cameron and others opponents are pressing for the vote to be held earlier.

Scotland and England united in 1707 to form Great Britain, but Scotland gained significant autonomy after voting in 1997 to set up the semiautonomous Edinburgh-based Scottish Parliament, which has power from education, health and justice and can make minor alterations to income tax.

London retains primacy on all matters relating to Britain as a whole _ including defense, energy and foreign relations.

Cameron's government and Salmond are already at odds over the date of the referendum, what will be on the ballot paper and whether 16- and 17-year-olds should be entitled to vote.

According to excerpts released in advance, Cameron planned to use a speech in Scotland to warn that independence could damage Britain's status in Europe, within NATO and put at risk the U.K.'s permanent seat on the U.N. Security Council.

"The fight is now under way for something really precious: the future of our United Kingdom. I am 100 percent clear that I will fight with everything I have to keep our United Kingdom together," Cameron planned to say, according to the excerpts.

"To me, this is not some issue of policy or strategy or calculation _ it matters head, heart and soul. Our shared home is under threat and everyone who cares about it needs to speak out," the text said.

Salmond insists that independence would bring greater prosperity, allowing Scotland to better exploit its energy resources.

"We have 25 percent of Europe's tidal power potential, 25 percent of its offshore wind potential and 10 percent of its wave power potential _ not bad for a nation with less than 1 percent of Europe's population," Salmond said Wednesday in a speech to the London School of Economics.

Cameron insisted Scotland would be safer and richer if it remained a part of the U.K., along with England, Wales and Northern Ireland. Both Wales and Northern Ireland also have administrations with some limited powers.

"We're stronger, because together we count for more in the world, with a permanent seat on the United Nations Security Council, real clout in NATO and Europe and unique influence with allies all over the world," Cameron planned to say.

"In an increasingly dangerous world we have the fourth-largest defense budget on the planet, superb armed forces and anti-terrorist and security capabilities that stretch across the globe and are feared by our enemies and admired by our friends," the excerpts read.

Cameron insists Scotland's 5 million people would be more prosperous as part of "the seventh-richest economy on the planet and one of the world's biggest trading powers."