President Barack Obama is weighing a possible naval cordon sanitaire around North Korea as one means of ratcheting up sanctions amid the fierce global criticism of this week's nuclear and missile tests by the reclusive communist country.

After the shock of its second nuclear test in three years — with a bare 25 minutes notice to the US — the regime yesterday rubbed salt into that diplomatic wound by test firing two short-range missiles, leaving the White House scrambling to stitch together an effective international response.

The North's show of defiance was “provocative, destabilising and a threat”, Susan Rice, Washington's ambassador to the United Nations, said, underlining that the Obama administration would not allow Pyongyang either to have its own nuclear weapons capability, or to export nuclear technology or materials.

She claimed that by carrying out the tests the regime had only succeeded in isolating itself even further, as demonstrated by the swift and unanimous Security Council response on Monday condemning the actions as a violation of the 2006 resolution forbidding North Korea to conduct nuclear tests.

All options were on the table, Ms Rice declared, repeating the stock US formulation at previous moments of impasse with Pyongyang.

But she specifically warned that Washington was ready to “step up” efforts “to intercept and interdict prohibited cargo from North Korea”.

But such stern talk only highlights the dilemma for US policymakers — as does the conflicting advice raining upon the administration from all sides.

Some foreign policy specialists urge the White House to pay more attention to Pyongyang, saying that the test was simply an expression of its frustration at being ignored thus far by the four-month-old Obama administration.

Other advisers take the opposite view, arguing that the most effective response is precisely to ignore the regime.

This school says that North Korea craves only attention and to be recognised as a ranking member of the nuclear club. Some North Korea watchers place their faith in China and to a lesser extent Russia, drawing encouragement from the unusually sharp condemnations of the test issued by Beijing and Moscow.

Others, however, warn that China, the North's key partner, above all desires to prevent a unified pro-US state on the Korean peninsula.

Some experts advocate resurrection of the stalled six-nation talks involving the North, the US, China, Russia, Japan and South Korea, but others insist the best option is direct bilateral talks between the US and North Korea.

In fact all these paths have been tried, and all in the past have failed. The Clinton administration in 1994 offered aid and other incentives to persuade Pyongyang to halt its nuclear programme only for the latter to renege on the deal.

The following Bush administration talked tough, branding the North a member of the “axis of evil”", but could not prevent it from throwing out UN weapons inspectors in late 2002 and conducting a first nuclear test four years later. By 2007 the Bush White House reversed course and reached an agreement whereby North Korea would dismantle its main nuclear plant — but Pyongyang reneged on that deal too.

US officials say the biggest threat is not of a North Korean nuclear missile launch but of exports to rogue states or even terrorist groups. Shipping inspections, authorised by a UN Security Council resolution after the 2006, would help counter this threat.

But they have not been applied, in part because of concern over Pyongyang's response to what it said it would regard as an “act of war”.