About 870 people have been resettled through the scheme so far.

Of those, 405 were in Papua New Guinea, 387 in Nauru and 78 in Australia.

Another 250 are provisionally approved to be resettled.

Home Affairs deputy secretary Marc Ablong expects the refugee quota to be reached by March or April next year.

But he said the coronavirus pandemic had delayed processing and the US signing its annual declaration outlining how many refugees it will accept.

"We expect that the US election will play into terms of them finalising that declaration," Mr Ablong told a Senate estimates hearing on Monday.

While all the refugees are expected to be moved by March or April, Mr Ablong reiterated that it was unknown if the pandemic would further delay when people could be resettled.

The swap deal was originally struck between former prime minister Malcolm Turnbull and the Obama administration, for up to 1250 people from Nauru and Manus Island to move to the US.

Australia pledged to take an unspecified number of Central American refugees.

Australian Associated Press