A US appeals court in San Francisco has upheld a decision blocking a proposed ban on travellers from six Muslim-majority countries entering the United States.

The proposed ban was initiated by president Donald Trump in the early days of his administration, but has been dogged by legal problems.

Ruling on a case brought by the state of Hawaii, the appeal judges found that the executive order violated existing immigration legislation

Trump has vowed to pursue the ban and the dispute may end up being decided in the US supreme court.

The executive order sort to ban people from Iran, Libya, Syria, Somalia, Sudan and Yemen from entering the United States for 90 days.

It also called for a 120-day ban on all refugees.