Crew union Nautilus International has warned about the effects on seafarers of US president Donald Trump’s travel ban.

General secretary Mark Dickinson has written to UK foreign secretary Boris Johnson, urging him to seek clarification on UK crew rights regarding shore leave, repatriation, transit and transfer in the US following the administration’s blocking of travel from seven mainly Muslim countries.

He expressed “deep concern” over the move and said he was “disturbed” at the implications.

“There are serious safety and welfare issues at stake if seafarers are unable to join or leave their ships as planned,” the letter says.

Nautilus said some owners are already being advised not to attempt crew changes in the US involving people from the affected countries

And the union fears already restrictive shore leave policies look set to become “even more extreme”

Nautilus points out that special protection for seafarers on shore leave, repatriation, transit and transfer is enshrined in the ILO 185 convention.

The Standard P&I Club said this week it did not believe ships carrying crew from the affected countries would be denied entry into US ports.