<span style="color: #222222;">US National Security Adviser John Bolton has said President Donald Trump is open to more talks with North Korea over denuclearisation. His comments came just days after South Korea's Yonhap News Agency and two US think tanks reported that North Korea has restored part of a rocket test site it began to dismantle after pledging to do so in a first summit with Trump last year.</span><br />'' <br />'' <span style="color: #222222;">Commenting on the reports, Mr Bolton said that the White House is going to study the situation carefully. He said it is too early to make a determination on the reports of the North Korean activity.</span><br />'' <br />'' <span style="color: #222222;">Mr Bolton on Tuesday had warned that new sanctions would be introduced, if Pyongyang did not scrap its nuclear weapons program. The denuclearization talks between the US and North Korea in the Vietnamese capital Hanoi ended with no agreement last week after Trump refused North Korean demand to lift all international sanctions.</span>