“We are running out of people to fuel the economic growth that we’ve had in our nation over the last four years,” he said. “We need more immigrants.”
He added that the Trump administration wants these immigrants to enter the US in a “legal fashion”.
Mr Mulvaney’s words mark a contrast to the hardline stance adopted by a number of top White House officials and, on occasion, the president himself, who warned that “our country is full” during a visit to the US-Mexican border in California last year.
However, Mr Trump has been inconsistent with his views on legal immigration.
In his more recent State of the Union address, he called for a system that rewards immigrants who “contribute to our economy, support themselves financially, and uphold our values”.
Such an approach echoes the policies adopted in Australia and Canada, with Mr Mulvaney admitting on Thursday that the Trump administration is eager to embrace a model closer to those nations.
“We are very interested in expanding that,” he reportedly said.
Efforts within the White House to push forward and develop such a system have been met with resistance from hardline immigration restrictionists, such as senior policy adviser Stephen Miller, who are eager to protect US workers from foreign competition.
Despite the ongoing debate on whether to promote or curb legal immigration, the US has been subject to a fierce crackdown on foreign workers and asylum seekers under Mr Trump.
The number of immigrant and non-immigrant visas issued since 2016 has notably decreased by more than 15 per cent, according to state figures, while efforts remain underway to construct a border wall between the US and Mexico.
Heeding calls from 31 states to end refugee admissions from Syria, Mr Trump has also slashed the total number of refugees the US accepts annually to just 18,000 this year, the fewest in history and down from a cap of 110,000 just two years ago.
A travel ban on citizens from a number of many Muslim-majority and African countries has been enforced too.