A top US diplomat has warned North Korea against any “provocative” act amid growing concerns that Pyongyang is preparing for a nuclear test. The US and its allies are seeking tighter sanctions after the launch of a long-range rocket last month.

Assistant Secretary of State for East Asian and Pacific Affairs Kurt Campbell reiterated that “provocative steps are to be discouraged” during his visit to Seoul where he met with senior officials, including South Korean President Park Geun-Hye.

Campbell said “intense deliberations” were under way at the UN Security Council on new sanctions over Pyongyang’s rocket launch last month which was internationally condemned as a disguise for banned missile tests.

The move violated UN sanctions over the North’s nuclear tests in 2006 and 2009, both of which came after long-range missile launches, AFP reports.

Analysis of satellite imagery showed North Korea was capable of carrying out a nuclear test at two weeks’ notice after repairing damage to its test facility, the US-Korea Institute at Johns Hopkins University said late last month following the rocket launch which Pyongyang said was purely for scientific purposes.

South Korean security experts said that Pyongyang could use a uranium device for the first time in its next nuclear test which is “sustainable for continuous testing”, although they are not sure how far North Korea has developed its uranium enrichment programme.

North Korea has vowed to bolster its war defenses against “US hostility” and claimed its right to build atomic weapons in the face of Washington’s “hostile policy”.