By Jon Leyne BBC Washington correspondent

Spot the difference. The United States is threatening war against one of the "axis of evil" because of its weapons of mass destruction.

For another of the "axis" countries, Washington is still agonising over whether to stop multi-million dollar aid payments.

The two countries, of course, are Iraq and North Korea.

The difference between them? North Korea is much further advanced in its programme to produce nuclear weapons.

The accusations of a double standard refuse to go away.

Oil shipments

In October North Korea reportedly admitted what US intelligence had suspected for some time.

The Bush administration has been accused of double standards

It has pressed ahead with a programme to produce nuclear weapons, despite a 1994 agreement renouncing the programme.

As part of that deal, negotiated by the Clinton administration, North Korea received massive help with its energy needs from the US, Japan, South Korea and the European Union.

That aid included oil shipments from the US, and assistance in building new nuclear reactors of a type which the North could not use to divert material for military purposes.

If America imposes economic sanctions, North Korea could regard that as an act of war

Commentator Kim Myong Chol

Yet the US has been slow to punish what appears a flagrant breach of North Korea's obligations.

An oil shipment on its way to the North is still being delivered. Finally, a couple of weeks ago, Washington decided to suspend future deliveries.

But work is still continuing on the nuclear reactor the Americans are helping to build in North Korea.

Playing safe

It is a situation that must provoke deep frustration amongst all those in the Bush administration who like to see the world in black and white.

Yet the government of Kim Jong-il has mastered the technique of making the most of what might appear an indefensible position.

Seoul is within easy range of thousands of North Korean missiles

Every time it is found out, it just threatens more action.

When the Americans considered ending the oil shipments, North Korea reportedly threatened to pull out of the nuclear non-proliferation treaty.

Now the fear is that Pyongyang will expel international inspectors stationed at a reactor in Yongbyon, who help prevent the country producing more weapons-grade nuclear material.

"And if America imposes economic sanctions - depending on the nature of the sanctions - North Korea could regard that as an act of war," said Kim Myong Chol, a commentator close to the North Korean government.

War 'unthinkable'

All but the most extreme hardliners in Washington know that war is unthinkable.

The South Korean capital, Seoul - one of the largest cities in the world - is within easy range of thousands of North Korean missiles.

Tens of thousands of US troops in South Korea are vulnerable.

And that is without even factoring in whatever weapons of mass destruction the North may already possess.

No wonder the US has received only half-hearted support for its policy of trying to isolate North Korea further.

It is much easier to talk tough from Washington, than it is from within missile range of this strange Stalinist country.

But even in the US itself, there appears little appetite for another confrontation, while Saddam Hussein is still so clearly in the sights.