LONDON -- Citing tensions with Iran and North Korea, Prime Minister David Cameron offered a strong defense of Britain's nuclear deterrent on Thursday, traveling to Scotland to challenge nationalists seeking independence who want to expel nuclear-armed submarines from Scottish bases.
Blending geopolitics with his opposition to Scottish independence, Mr. Cameron welcomed home the crew of a nuclear-armed submarine based in western Scotland and told defense industry workers that their jobs were more secure in a united Britain.
Mr. Cameron spoke as a sense of crisis built on the Korean Peninsula and the United States said it was accelerating the deployment of an advanced missile defense system to Guam in the next few weeks to protect American naval and air forces in case North Korea carries through its threatened missile attack.
Britain maintains a force of four nuclear submarines that patrol year-round carrying Trident missiles. But lawmakers are locked in a debate about the cost of replacing them at a time when Scottish nationalists, committed to nuclear disarmament, say they will not allow the submarines to be based in an independent Scotland.
Scots ages 16 and over living in Scotland are eligible to vote in a referendum on independence in September 2014, but the ballot is already tugging at British politics.
In an article in The Daily Telegraph, published before he went to Scotland, Mr. Cameron said the global nuclear threat had "if anything, increased" since Britain built a nuclear deterrent over 60 years ago during the cold war.
"I know there are some people who disagree with our nuclear deterrent and don't want us to renew it," he said. "There are those who say that we don't need it any more, because the cold war has ended. There are those who say we can't afford Trident any more, so we either need to find a viable cheaper option, or rely on the United States to protect us."
But "the nuclear threat has not gone away," he added. "In terms of uncertainty and potential risk it has, if anything, increased."
With Iran pursuing nuclear ambitions and North Korea testing nuclear devices and missiles, Mr. Cameron said, "does anyone seriously argue that it would be wise for Britain, faced with this evolving threat today, to surrender our deterrent?"
He described the North Korean government as "highly unpredictable and aggressive."
In his remarks to defense industry workers in Scotland, Mr. Cameron said, "Being part of the U.K. opens doors for the Scottish defense industry around the globe."
"Scotland counts for more on the world stage because it is part of the United Kingdom and Scottish defense jobs are more secure as part of the United Kingdom," he said. "The business community tell me that they want certainty. And I want to offer that certainty by saying that I remain absolutely committed to the defense of the United Kingdom and to the future of defense jobs in Scotland."
Angus Robertson, the defense spokesman of the Scottish National Party, said the prime minister's promises to support the defense industry in Scotland represented "just the same old, same old" pledges from British governments that had left Scotland at an economic disadvantage.
"It just shows that when it comes to defense, Westminster isn't working for Scotland," said Mr. Robertson, referring to the seat of British power in London, "and an independent Scottish Parliament would take far better defense decisions for Scotland."
This article originally appeared in The New York Times.