US President Donald Trump has lashed out at China for undermining its work with North Korea, as criticism over progress on denuclearisation mounts. In a series of tweets he also said the US should not be spending on war games with South Korea, but if it did restart them they would be "bigger than ever". The US called a halt to the military exercises which routinely infuriate Pyongyang after landmark talks in June. But days ago his own defence secretary said military exercises might continue. The ongoing debate about the war games comes as many observers say North Korea is not moving fast enough to dismantle nuclear or rocket sites following the summit between Trump and North Korean leader Kim Jong-un. Trump's tweets appear to place the blame for these challenges squarely on China, but he also goes on to praise his personal ties with the leaders of both North Korea and China. The confusing blend of criticism, praise and veiled threat comes as Washington faces mounting pressure to deliver results following those unprecedented talks. Immediately after the summit Trump announced there was "no longer a nuclear threat from North Korea". Just days ago, Washington called off a trip to North Korea by US Secretary of State Mike Pompeo with the president arguing that insufficient progress had been made in dismantling the North's nuclear programme. In the latest statement released on Twitter, Trump says North Korea was "under tremendous pressure from China because of our major trade disputes with the Chinese government". It also accuses Beijing of providing North Korea with "considerable aid," suggesting Chinese help was softening the blow of international sanctions on the regime in Pyongyang. "This is not helpful!" Trump's tweet says. The US President goes on to insist his personal relationship with Kim Jong-un remained "a very good and warm one" and that hence there was no reason to restart the "war games" with the South. But he added that if they did restart, the exercises would be "bigger than ever". Referring back to the trade dispute with Beijing, Trump says he remains optimistic it can be resolved by himself and China's "great President Xi Jinping". (BBC)