Scottish leader Alex Salmond has set Sept. 18, 2014, as the date for an independence referendum that could radically alter the shape of the United Kingdom, calling it a historic opportunity to create a better country.

Salmond announced the date of the long-awaited vote to the Scottish Parliament on Thursday, saying it would be a day when Scotland takes "responsibility for our country, when we are able to speak with our own voice, choose our own direction and contribute in our own distinct way."

Salmond's nationalist party wants Scots to become independent, ending more than 300 years of union with England. The Scottish leader argued that becoming a separate country would give Scotland a "new, more modern" relationship with other nations of the U.K.

"Next year, the choice facing the people is one of two futures. A `No' vote means a future of governments we didn't vote for, imposing cuts and policies we didn't support. A `Yes' vote means a future where we can be absolutely certain, 100 percent certain, that the people of Scotland will get the government they vote for," he told parliament.

The British government is campaigning to keep Scotland in the United Kingdom, saying independence would create a deeply uncertain future.

Scotland and England united in 1707 to form Great Britain, but Scotland gained significant autonomy after voting in 1997 to set up the Edinburgh-based Scottish Parliament, which has power over areas including education, health and justice. London retains control of defense, energy and foreign relations.