U.S. National Security Adviser John Bolton has said North Korea's latest missile launches are a violation of UN Security Council resolutions.

Japan's Kyodo news agency said on Saturday that Bolton made this remark while speaking to reporters in Tokyo.

Kyodo said it's the first time a senior U.S. official has called the missile launches earlier this month a violation of UN sanctions on Pyongyang.

Bolton said the U.S. remains open to talks with North Korea, but the regime is unresponsive.

He said President Trump has held the door open for the North Korean leader and the next step is for Kim Jong-un to walk through it. 

He added that Stephen Biegun, Trump’s special envoy for North Korea, “can’t wait to talk to his North Korean counterpart, but they have not responded.” 

Bolton said when Trump meets Japanese Prime Minister Shinzo Abe for summit talks on Monday, the two will discuss measures to make sure sanctions are maintained.