(Reuters) – A federal judge in Hawaii extended his halt of U.S. President Donald Trump’s travel ban on citizens from six Muslim-majority countries.

U.S. District Judge Derrick Watson, who stopped the ban from taking effect this week, on Friday converted his temporary restraining order to a preliminary injunction.

Watson’s ruling, issued in Honolulu, applies only to the six Muslim-majority countries of Iran, Libya, Syria, Yemen, Somalia and Chad, although the ban, announced in September, also limits travel from North Korea and Venezuela.

Trump has said the restrictions are needed to tighten security and prevent terrorist attacks, and his administration reserved its right to appeal the injunction.

Opponents say the ban violates the U.S. Constitution because it discriminates against Muslims while overstepping the bounds of U.S. immigration law by discriminating by nationality.