Liberia has said it would take in a Salvadoran man at the centre of a deportation row denounced by opponents of President Donald Trump's immigration crackdown.

Liberia's government said in a statement on Saturday that it would receive the man, Kilmar Abrego Garcia, "on a strictly humanitarian and temporary basis, following a formal request from the government of the United States of America."

The US government said in a court filing on Friday it planned to deport Abrego Garcia to the "thriving democracy" of Liberia within a week.

Trump's government accuses him of being a violent MS-13 gang member involved in smuggling other undocumented migrants.

Garcia has no connection to Liberia: lawyer

He was already wrongly deported to El Salvador in March, then sent back to the United States in June.

A lawyer for Abrego Garcia said the man had no connection to Liberia, and that floating that as a deportation destination was "unconstitutional."

The lawyer, Simon Sandoval-Moshenberg, said Costa Rica was willing to take him in as a refugee.

Liberia said the decision to receive Abrego Garcia was arrived at "after extensive consultations" and tracked with its commitment to principles of "human dignity, international solidarity, and compassion in times of distress."

Liberia noted its "longstanding friendship" with the United States, with which it would "continue to engage... to ensure that all assurances and arrangements between the two countries are fully observed."