The US immigration enforcement surge in Minnesota will end, President Donald Trump's border tsar told reporters on Thursday.

Tom Homan said Trump had approved his request to conclude the operation, adding he would stay in Minnesota "a little longer to oversee the drawdown, to ensure its success".

Homan said Operation Metro Surge had resulted in many illegal immigrants who had committed violent crimes being detained for deportation. But the surge also sparked nationwide protests after two US citizens, Renee Good and Alex Pretti, were killed by immigration officers.

After the news conference, top officials appeared on Capitol Hill to testify about Trump's immigration crackdown.

Officials in Minnesota have been able to "greatly reduce the number of targets" for immigration enforcement, Homan said, adding that Operation Metro Surge was a "great success".

More than 4,000 undocumented immigrants, whom Homan referred to as "illegal aliens", had been arrested, including men he said were convicted of rape and other sexual misconduct, he said.

Homan said that Immigration and Customs Enforcement (ICE) has always had a presence in Minnesota and will continue to have one.

The reduction in force comes after what Homan described as an unprecedented level of cooperation between federal agents and local law enforcement.

He said Minneapolis law enforcement increased their crackdown on protesters he called public safety threats and local jails have been more willing to notify ICE of the release date for individuals the agency was targeting.

Following the fatal shooting of Alex Pretti, President Donald Trump dispatched Homan to Minneapolis to oversee the surge, sidelining the operation's leader Greg Bovino.

Last week, Homan announced he was removing 700 immigration agents from the state, leaving around 2,000 federal officers there, after receiving greater cooperation from local leaders, and that he was working to cut their presence to where it was before the operation started in December.

On Thursday, he said Minnesota has become "less of a sanctuary state" and he had meetings over the last few weeks with Minneapolis Mayor Jacob Frey and Minnesota Governor Tim Walz, whom he said he asked to "tone down the rhetoric".

Sanctuary cities and states have passed laws to limit the support they give to enforcement of federal immigration authorities.

While Homan and the Trump administration blamed escalating tensions in Minneapolis on the rhetoric from Minnesota officials, Frey and other critics of the immigration crackdown said ICE tactics, such as stopping and searching people, were at fault.