Raids to detain and deport migrants living in the US without permission are set to begin on the first full day of President-elect Donald Trump's new administration, sources have told the BBC's US partner CBS.

It is unclear where the operations - threatened by Trump's "border tsar" Tom Homan - could begin.

Earlier reports indicated deportations would start in Chicago, a city with a large migrant population, as early as Tuesday.

But Homan told the Washington Post on Saturday that the Trump administration is reconsidering after the location was leaked.

Trump has vowed to oversee the largest deportation programme in US history, and Homan has said criminals and gang members will be prioritised in such raids.

Homan told the Post that the administration's enforcement goals are broader than just Chicago.

"ICE will start arresting public safety threats and national security threats on day one," he said. "We'll be arresting people across the country, uninhibited by any prior administration guidelines. Why Chicago was mentioned specifically, I don't know."

In an interview with Fox News this week, the border tsar promised a "big raid" across the country. He has previously said Chicago will be "ground zero" for the mass deportations.

Homan expanded on the administration's plans on Fox News over the weekend,saying the deportations will not be "raids", but "targeted enforcement operations".

He described these efforts as "well planned".

"When ICE goes out, they're going to know exactly who they're looking for and pretty much where they'll find them," Homan said.

He said he expects deportation flights to leave in the first week of Trump's presidency and anticipates daily lawsuits for deportation efforts from organisations like the American Civil Liberties Union.

"I'm sure we'll be sued, but bring it," he said.

Trump, a Republican, also promised mass deportations ahead of his first presidential term back in 2017 - though he ended up removing about half the number of immigrants that President Barack Obama, a Democrat, did in his first four years.

The 47th president is coming into office with widespread support for his border policies. A New York Times and Ipsos poll published on Saturday found 55% of Americans either strongly or somewhat support such mass deportations.

The Immigration and Customs Enforcement (ICE) agency deports illegal migrants all the time.

However, the operation to be launched after Trump's inauguration on Monday is expected to target so-called "sanctuary" cities that limit co-operation with federal immigration officials, two sources familiar with the plans told CBS.

ICE officials in the Chicago area recently asked agents to join this week's planned raids without notifying heads of the agency in Washington DC, according to CBS.

New York, Los Angeles, Denver and Miami are also due to be targeted with raids, the Wall Street Journal reported, citing unnamed sources familiar with the plans.

Some reports suggest that Trump could do away with a longstanding policy that has made churches off-limits for ICE arrests.

At a church in a mostly Latino neighbourhood of Chicago, worshippers shared their concerns with the BBC.

"I'm scared, but I can't imagine what people without papers are feeling," said D Camacho, a 21-year-old legal immigrant from Mexico who was in the congregation at Lincoln United Methodist Church in the Pilsen area last Sunday.

Reverend Emma Lozano said: "If someone with five children gets taken, who will take the children in? Will they go to social services? Will the family be divided?"

The rules under Democratic President Joe Biden were that ICE was generally to prioritise the arrest of illegal migrants who were serious criminals, had crossed the border recently or posed a national security threat.

While Trump's team has signalled that it will begin with migrants who had committed crimes, all illegal migrants - including those who have lived and worked in the US for many years and have no criminal history - may be more likely to be arrested and deported.

Immigration raids at construction sites where undocumented migrants are often employed are also expected to resume, after being discontinued by the Biden administration, according to CBS.

However, the operation could pose difficulties for officials - with limited custody space to hold detainees.

At the same time, the Laken Riley Act - named after a college student who was murdered last year in Georgia by a Venezuelan illegal migrant who was previously arrested for shoplifting - is expected to be passed by Congress next week.

The proposed legislation will require the federal government to detain migrants living in the US illegally who are suspected of criminal activity.