PRESIDENT Barack Obama has rounded on former vice-presidential candidate Sarah Palin and her criticisms of his nuclear defence policy, calling the former Alaska governor "not much of an expert on nuclear issues".
Mr Obama's comments came when asked for a response about Ms Palin's claim that the president was behaving like a child in a playground fight who said, "Go ahead, punch me in the face and I'm not going to retaliate. Go ahead and do what you want to with me."
"I really have no response," Mr Obama said. "Last I checked, Sarah Palin's not much of an expert on nuclear issues."
Mr Obama made the remarks in Prague, where he signed a treaty with Russian president Dmitry Medvedev that orders both nations to shrink their nuclear arsenals. That deal must still be ratified by the Russian parliament and the US Senate.
Ms Palin, the 2008 Republican vice-presidential nominee and a potential presidential candidate in 2012, was referring to another development on the nuclear front this week, a rewriting of American nuclear strategy.
Among many other elements of that new plan, the US makes plain that if a non-nuclear nation is in compliance with an international non-proliferation treaty, the United States will not threaten or use nuclear weapons against it.
If such a state were to use chemical or biological weapons against the US or its allies, it would face a potentially devastating conventional military strike by the US, but not a nuclear one.
North Korea and Iran were not included in that pledge because they do not co-operate with other countries on non-proliferation standards.
"It's unbelievable," Ms Palin said.
"No administration in America's history would, I think, ever have considered such a step that we just found out president Obama is supporting today."