American Catholic bishops have expressed concern following the introduction of a revised travel ban.

Following President Donald Trump's latest executive order banning arrivals from six majority-Muslim nations, Bishop Joe S Vasquez of Austin, Texas, chairman of the US bishops' Committee on Migration, said Trump's new order still puts vulnerable populations at risk.

"We remain deeply troubled by the human consequences" of the order, he said in a statement. "While we note the administration's efforts to modify the executive order in light of various legal concerns, the revised order still leaves many innocent lives at risk."