>> All sides upping the ante on North Korea, as a US naval fleet heads to the Korean Peninsula, a Chinese envoy has arrived in Seoul for talks on Pyongyang's weapons program. Tension is simmering over whether the North could be readying its sixth nuclear test. With satellites detecting movement at a site used for previous trials.
Questions are swirling over the idea of possible US military action against Pyongyang. Reuters' James Pearson is on the story from Seoul.>> Following Trump's attack on Syria people are obviously thinking perhaps the same thing could happen with North Korea. But North Koreans got nuclear weapons now or at least it has a nuclear-capable program makes it a very, very different kind of target than Assad, Syria.
I think on top of that, we've got South Korean, Japanese officials here saying this week that where it to happen, they would try and put a stop to it.>> Adding to the tension and questions of when another North Korean test could come, timing. Weapons tests have been known to happen on days of national celebration, and there's a big one coming up this week.
>> April 15th is like North Korea's Christmas. They celebrate the birth of Kim Il-Sung, the founding president. And it's basically the biggest holiday in the country. We're expecting to see a military parade in Pyongyang. And in the past, they've also done things like test long range rockets ahead of that holiday.
So, everybody's basically watching Pyongyang at the minute, just in case there is some kind of, what would be viewed on the outside at least, a provocation.>> Over the weekend, US Secretary of State Rex Tillerson said the Syria strike was a warning, and that a response to North Korean weapon use is likely if it poses a danger.
The USS Carl Vinson's trip back to the Korean Peninsula is a quick return. It had just taken part in ongoing US-South Korean military drills that Pyongyang calls preparation for war.