The United States is giving China a "mission impossible" by insisting it exert pressure on neighboring North Korea to halt its nuclear program or face US consequences, Beijing's ambassador said Thursday.

"There is one thing that worries me a little bit, and even more than a little bit, is that we're very often told that China has such an influence over DPRK and we should force the DPRK to do this or that," Cui Tiankai told a Washington think-tank.

"Otherwise the United States would have to do something that would hurt China's security interests. You see you are giving us a mission impossible."

Tiankai, who has been China's envoy to Washington since April 2013, said he did not "think this was very fair, I don't think this is a constructive way of working with each other."

Washington has been leaning on Beijing to take a larger role in reining in the reclusive regime of North Korean leader Kim Jong-Un.

Cui told an audience at the United States Institute of Peace that Beijing was very worried by the threat of nuclear arms on the Korean peninsula and the risk of another war, armed conflict or chaos.

Tensions have been rising on the peninsula following a series of threats by Pyongyang in protest at ongoing Seoul-Washington military drills.

The North has staged a series of rocket and short-range missile tests since last month, as well as its first mid-range missile launch since 2009.

The two Koreas traded fire across their tense Yellow Sea border last week, with the shells landing in the sea.

"The peninsula is just at our doorstep, any chaos, any armed conflict there will certainly have cross-border effects on China," Cui said.

"But this problem cannot be solved by China alone. We need cooperation among the relevant parties."

- 'Stop Taiwan arms sales' -

The ambassador also called for deeper military-to-military ties between the United States and China, even as US Defense Secretary Chuck Hagel tours the Asia region on a trip which saw him visit China.

Despite progress over the past few years, strengthened military relations were needed for the new model of relationship which the two nations have agreed to set up.

"Mil-to-mil relations would be an indispensable part of this new model," Cui said, arguing that otherwise "this new model would not be effective, and I don't think it would stand up for very long."

Hagel and Chinese military chiefs traded warnings and rebukes on Tuesday as they clashed over Beijing's territorial disputes with its neighbors.

But Cui said the "direct exchanges" in Beijing were "not a bad thing" as both sides got to express their views.

He also argued that the US military could "greatly enhance mutual understanding" if it would stop its reconnaissance activities in China's exclusive economic zone, which extends over areas disputed with many of its neighbors.

"Still better if you could stop arms sales to Taiwan. That would help us a great deal," Cui said, with a wry smile, knowing that such a move would break pacts between the island and Washington.

Taiwan buys weaponry mainly to deter any attack by China. The two sides split in 1949 but China still sees the island as part of its territory awaiting reunification.

In 1979, the United States switched recognition from Taipei to Beijing in a seismic diplomatic shift. Congress at the same time approved the Taiwan Relations Act, which requires the United States to ensure Taiwan's self-defense.