A US federal appeals court has rejected President Donald Trump's attempt to reinstate his ban on citizens from seven mainly Muslim countries. The 9th US Circuit Court of Appeals said it would not block a ruling by a Seattle court that halted the order. Mr Trump responded with an angry tweet saying national security was at risk and there would be a legal challenge. It was unclear whether he intended to file an appeal to the Supreme Court or keep fighting the case in Seattle. In its 3-0 unanimous ruling on Thursday, the appeals court said the government had not proved the terror threat justified reviving the ban.