Pyongyang. North Korea is marking the 101st anniversary of the birth of founding father Kim Il-sung as tensions continue over the country’s nuclear programme.Leader Kim Jong-un visited the mausoleum of his grandfather and his father Kim Jong-il in Pyongyang, the official KCNA news agency reports.In recent weeks, Pyongyang has threatened to attack South Korea, Japan and US bases in the region. The US has ruled out holding any more "artificial talks” with the North."We can’t continue this charade and we cannot have a policy of rhetoric about denuclearisation. There have to be real steps here,” Secretary of State John Kerry said.Kerry said the North’s main diplomatic ally, China, had made a very strong statement criticising Pyongyang for its recent behaviour. Yesterday, Jung-un was at the Kumsusan mausoleum to pay "high tribute and humblest reverence” to the country’s former leaders, KCNA reports.There is speculation that the North will use Kim Il-sung’s birthday for a missile launch.At this time, last year, it launched a rocket with the stated aim of putting a satellite into orbit to mark the 100th anniversary of Kim Il-sung’s birth. The rocket broke up shortly after take-off.The UN Security Council condemned the launch, which many outside the country saw as an illegal test of long-range missiles.Kim Il-sung died in 1994, and was succeeded by Kim Jong-un’s father Kim Jong-il, until his death in 2011.