The Obama Administration is gravely concerned about North Korea's nuclear programme, which is far more advanced than Iran's. Yet its policy toward Pyongyang is little different than the course followed by George Bush in his second term and appears increasingly ineffective.

Laying out that policy on Wednesday during congressional testimony Hillary Clinton, the US Secretary of State, urged North Korea to refrain from provocative acts and return to six-party talks, which Pyongyang abandoned in December.

Referring to the willingness of Russia, China, Japan, South Korea and the US to restart the talks, Mrs Clinton said: "I think the strong support that we see among the parties against what North Korea's doing will eventually yield fruit."

Yet many believe that there is very little the US can do to stop North Korea's programme, and its huge advances in developing a nuclear arsenal will only encourage Iran that it can - or should - follow suit.

In recent weeks, Pyongyang has expelled international nuclear inspectors and on April 5 it launched a rocket that analysts believe was part of its programme to manufacture a delivery system for a nuclear warhead.

Some in the US, such as Madeleine Albright, Bill Clinton's former Secretary of State, believe that North Korea's recent provocations have been attempts to push Mr Obama's Administration into bilateral talks. He has only gone so far as to say that he will seek bilateral engagement while continuing the six-party talks.

By Tim Reid, The Times, April 24, 2009