US President Barack Obama said that China was taking a tougher line against North Korea's nuclear program as he credited new President Xi Jinping with taking more responsibility in the world.

"We've seen the Chinese take more seriously the problem of constant provocation and statements from the North Koreans -- rejecting the nuclearization," Obama told "The Charlie Rose Show."

"In the past, they would try to paper over the intentions," he said in the interview broadcast Monday.

"They kind of pushed those problems aside. We're seeing, I think, an interest and a willingness to engage with us in a strategic conversation around those things," he said.

China is the main economic and diplomatic supporter of Kim Jong-Un's isolated regime, which brazenly defied Beijing's warnings by carrying out its third nuclear weapons test in February.

China took the rare step of cracking down on North Korean bank accounts as part of new UN-led sanctions, although many experts doubt Beijing would go so far as to risk a collapse of the impoverished state separating it from US ally South Korea.

Obama said that he saw a gradual movement by China to take more responsibility in global affairs since Xi assumed power in March. Obama held two days of informal talks with Xi on June 7-8 at a California desert resort.

"My impression of President Xi is that he has consolidated his position fairly rapidly inside of China, that he is younger and more forceful and more robust and more confident, perhaps, than some leaders in the past," Obama said.

S. Korea top North envoy heads to US
Seoul (AFP) June 18, 2013 - South Korea's top envoy on North Korea left Tuesday for a meeting in Washington with his US and Japanese counterparts, two days after Pyongyang proposed direct, high-level talks with the United States.

After Washington, Cho Tae-Yong will travel on to Beijing -- where he is likely to overlap with a visit by North Korea's chief nuclear negotiator, Kim Kye-Gwan, to the Chinese capital.

Speaking to the South's Yonhap news agency before his departure, Cho said it was important to retain a clear perspective on the North's recent moves towards dialogue after months of military tensions.

"At this point, it is important for relevant parties to rebuild trust so that progress can be made toward the goal of denuclearising North Korea, rather than talks for talks' sake," Cho said.

The North's offer of direct denuclearisation talks with Washington -- bypassing any initial dialogue with Seoul -- was seen by many analysts as a bid to drive a wedge between the United States and its South Korean ally.

The US responded by insisting that Pyongyang first demonstrate its willingness to abandon its nuclear weapons programme.

North and South Korea had been scheduled to hold their first high-level talks for six years last week, but they were cancelled after a row over protocol.

In Washington, Cho will meet with the US and Japanese special envoys on North Korea, Glyn Davies and Shinsuke Sugiyama, but said he had "no plan" to meet Kim Kye-Gwan in Beijing.

South Korean President Park Geun-Hye is due to make her first visit to China later this month for a summit with President Xi Jinping.