The Trump administration held secret talks with Iran about deporting Iranians even as the war between the two countries continued, according to court documents unsealed in a US immigration case.

Filings show that as recently as mid October the administration said it had plans to remove Iranians through an unnamed third country, though it was unclear when any such transfers would begin. The case arises from a lawsuit that alleges violations of national immigration rules.

A federal judge ordered the government to give the court 24 hours' notice of any finalised plan to deport Iranians to Iran or to any other country, and five days' written notice before carrying out such a removal. During a hearing the judge pressed justice department lawyers on the logic of sending people back to a country the president has described as lawless and as an enemy of the United States, warning of a serious threat of death. The government attorney replied that the United States was executing lawful removal orders.

The disclosure lands while combat and diplomacy with Tehran both remain active, and while Stephen Miller, a chief architect of hardline deportation policy, has just been named White House chief of staff. Public records do not show how many people were targeted, which third country was discussed, or whether Iran agreed to accept returnees. They do show a wartime administration pursuing immigration enforcement against nationals of a state it is fighting, under court supervision that now requires advance notice before any flight.