Glyn Davies, the US special envoy on North Korea policy, was speaking to reporters in South Korea's capital Seoul when he said:
Whether North Korea tests or not, it's up to North Korea. We hope they don't do it, we call on them not to do it. It will be a mistake and a missed opportunity if they were to do it.
More top news
Rescue workers are at the site Sunday morning trying to cut open mangled coaches.
Despite chilly temperatures it will be a mostly dry day, and milder than yesterday.
The Sunday Times alleges a missile malfunctioned after launch during a routine test of the UK's nuclear deterrent last year.