US President Donald Trump is expected to make an announcement this week about the existence of any tapes of conversations between him and former FBI director James Comey, the White House has said.

"The president has said that he will make an announcement on this. I expect it this week," White House spokesman Sean Spicer told reporters at a news briefing.

Mr Spicer was responding to a question about whether there are tapes of the conversations with Mr Comey, whom Trump fired last month, and whether they would be turned over to the House of Representatives Intelligence Committee.

The committee is probing allegations of Russians meddling in the 2016 US election and possible collusion with the Trump campaign.

Meanwhile Mr Trump has said that Chinese efforts to persuade North Korea to rein in its nuclear program have failed, ratcheting up the rhetoric over the death of an American student who had been detained in North Korea.

Mr Trump had held high hopes for greater cooperation from China to exert influence over North Korea, leaning heavily on Chinese President Xi Jinping for his assistance.

The two leaders had a high-profile summit in Florida in April and Mr Trump has frequently praised Mr Xi and resisted criticising Chinese trade practices.

"While I greatly appreciate the efforts of President Xi & China to help with North Korea, it has not worked out. At least I know China tried!" Mr Trump wrote in a tweet.

It was unclear whether his remark represented a significant shift in his thinking in the US struggle to stop North Korea's nuclear program and its test launching of missiles or a change in US policy toward China.

But it was likely to increase pressure on the Chinese government ahead of a US-China Diplomatic and Security Dialogue tomorrow.

The talks will pair US Secretary of State Rex Tillerson and Defense Secretary James Mattis with China's top diplomat, State Councilor Yang Jiechi, and General Fang Fenghui, chief of state of the Peoples Liberation Army.