Trump and the pontiff have already clashed at a distance on issues including migration and climate change.

The remarks are the latest indication of mounting U.S. concern about Pyongyang's advancing missile and nuclear weapons programs.

The dollar index held steady against a basket of six currencies at 97.321 after bouncing 0.4 percent the previous day.

A spokesman said martial law would be in place for 60 days, in line with constitutional limits on the use of military rule.

The attacker set off his improvised bomb as crowds streamed out of the Manchester Arena after a pop concert by Ariana Grande.