Iran, with its first launch of a home-made satellite Monday, and North Korea, by fomenting rumours about an imminent missile test, have forced US President Barack Obama's administration to take a strong stand.

In part at least to show that he will not be intimidated in the case where the two "rogue states", to use a term coined by the US neo-conservatives, might want to test Washington's resolve.

Yet their actions have different causes, according to experts.

Andrew Brooks, at London's Royal Institute of International Affairs, said the satellite launch to mark the 30th anniversary of the Islamic revolution is "a simple act of propaganda within the framework of a civilian programme."

"This will not have any impact whatsoever on their nuclear capability," he said.

Tehran's goal lies elsewhere.

He said they want to put a television satellite into orbit "that could carry the message throughout the Middle East."

"If you can spread the word of the Ayatollah, the word of (President Mahmoud) Ahmadinejad, that is much more powerful than a ballistic missile they would never be able to use."

Brooks played down concerns that the satellite launcher, the home-built Safir-2 rocket, would bring massive new reach to the Islamic republic's nuclear capabilities.

"All of that is totally different from a nuclear-headed long-range missile, able to hit Western Europe or United States, that Iran would not have for at least 20 years," he said.

Cedric Poitevin, a researcher at the peace information group (GRIP) in Brussels, said that despite past links it would be mistaken to see the actions of Tehran and Pyongyang as coordinated.

"Given past cooperation between these two countries on missile technology, it is tempting to draw a link between the Iranian satellite and a possible future North Korean ballistic test, but this would be irrelevant," he said.

"North Korea is playing for its survival. Its nuclear arsenal is its only exchange currency," he said. "Given that, North Korea has an interest in dragging negotiations out ... to the greatest advantage."

Nuclear disarmament talks with the North, involving the United States and four regional powers, are deadlocked over how Pyongyang's atomic disclosures should be verified.

Washington warned North Korea Tuesday that any test of its longest-range missile would be seen as "provocative."

But with questions hanging over the health of leader Kim Jong-Il and his possible successor, a missile test could be part of a strategy to show that the regime is still strong, Poitevin said.

In any case the moves come just as the new US administration readies to make its first public declarations on its missile shield extensions into Europe, which have angered Russia.

US officials have suggested the shield -- including missile interceptors in Poland linked to a radar in the Czech Republic -- could come under review, meaning a de-facto slowdown of the project.

That announcement, welcome news for Moscow, could come at an international security conference in Munich, southern Germany, to be attended by top US officials including Vice President Joe Biden, starting Friday.

But again, the experts said the actions of Iran and North Korea are unlikely to be aimed at driving a wedge between Moscow and Washington, just as Obama appears to be reaching out.

"My guess is that both North Korea and Iran are probably too self-regarding to hatch such an oblique strategy for discord between US and Russia," said Nick Witney, at the European Council on Foreign Relations.

"Especially when 'success' would see the US pressing on with a missile shield which might ultimately invalidate their own weapons."

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