The Deputy First Minister spoke of her commitment to nuclear disarmament at a CND Scotland rally in Glasgow's George Square today.
She described the planned replacement of the UK's Trident nuclear deterrent, based on the Clyde, as a "monumental mistake", telling the crowd that the chance for a nuclear weapon-free Scotland was "now or never".
She said: "For all of my political life I have been committed to the pursuit of nuclear disarmament - indeed, I was in the CND before I was in the SNP.
"But for all of my life I have lived under the shadow of the United Kingdom's nuclear arsenal, based only a few miles away on the Clyde.
"It is, and always has been, unacceptable to me that such devastation could be launched from Scotland. But it is clearer than ever that all of the warm words from successive UK governments about nuclear non-proliferation are just that - warm words.
"There are less than six months to go until Scotland decides what kind of country we want to be. One of the biggest choices we face is whether Scotland remains home to weapons of mass destruction, or whether we take this opportunity to remove them once and for all.
"Just think about it - as the world's newest country, one of the first things an independent Scotland will have the chance to do is rid itself of weapons of mass destruction.
"I cannot think of any more powerful statement we can make to the world about what kind of country we will be, and what our place in the world will be.
"With all of the main Westminster parties making it absolutely clear that they intend to make the monumental mistake of renewing Trident, September's referendum is the only real chance we have of ridding ourselves of nuclear weapons.
"Put simply, it is now or never."
Today's march and rally was part of the CND's Spring Walk which left the Scottish Parliament on Tuesday and is scheduled to arrive at Faslane on Monday afternoon.
The group said around 50 campaigners were undertaking the almost 100-mile trek across central Scotland.
Earlier this week the CND welcomed First Minister Alex Salmond's denial that Trident would be used as a bargaining chip in any post-Yes vote negotiations on currency.
The Conservatives are currently committed to a like-for-like replacement for the existing four-boat fleet if they win the next general election, at an estimated cost of £20 billion.
Labour also supports a continuous-at-sea-deterrent (CASD) but following a review of the options for renewing the deterrent last year, the Liberal Democrats said that CASD was no longer necessary in the post-Cold War era and they would only build three new submarines.