BEIJING (Reuters) - China has hit back in unusually strong terms against repeated calls from the United States to put more pressure on North Korea over Pyongyang's nuclear and missile programs.

A Chinese Foreign Ministry spokesman saying attempts to blame Beijing undermine international efforts to resolve the issue.

"Recently, certain people, talking about the Korean peninsula nuclear issue, have been exaggerating and giving prominence to the so-called 'China responsibility theory'. I think this either shows lack of a full, correct knowledge of the issue, or there are ulterior motives for it, trying to shift responsibility," said Chinese Foreign Ministry spokesman Geng Shuang.

US President Donald Trump has expressed impatience that China has not done enough to leverage its close economic and diplomatic ties to put pressure on Pyongyang.

But Mr Trump took a markedly conciliatory tone at a meeting with Chinese President Xi Jinping at the G20 summit over the weekend.

"I am sure that we will come to a successful conclusion," he said.

North Korea's nuclear ambitions were on stark display, testing an intercontinental ballistic missile last week that some experts believe could deliver a warhead to Alaska and parts of America's Pacific coast.

The Pentagon said it had a successful test of its own of a missile defence system known by the acronym THAAD.

This was the first test of the system against an incoming intermediate-range ballistic missile.

Earlier this year the US deployed THAAD to South Korea, a move drawing fierce criticism from China, which fears the system's high-powered radar can probe its territory.