The officials with the immigration and the application of US customs (ICE) should have carried out raids in several large cities on Sunday as part of a radical repression of immigration, on the orders of the President of the States United Donald Trump.
They will look for up to 2,000 people who have been ordered expelled but have not left the United States.
Officials from the administration said that the national operation, under way at least until Thursday, would produce around 200 arrests based on previous repression.
The White House insists that the raids will focus on the criminals already present in the deportation lists, but there are concerns even for undocumented migrants who respect the law.
New York Mayor Bill de Blasio tweeted Saturday that he received news that the crackdown had already begun in his city, in Brooklyn and Harlem.
The Democratic mayor has stated that his city will not cooperate with the ICE.
The raids were expected in Denver, Los Angeles, San Francisco, Baltimore, Chicago, Atlanta, New York, Houston and Miami, according to supporters of immigration reform.
Defenders in some cities have instructed migrants about their rights, including not responding if agents knock on the door unless they show a warrant signed by a judge.
Texas Democratic representative Sheila Jackson Lee said today that many Houston religious leaders will offer shelter on Sunday.
On Friday, Trump confirmed that the plan, intended to discourage a wave of Central American migrants, was on its way after a delay.
Trump revealed the operation on Twitter last month and then postponed it. It is unusual for the US government to announce deportation operations ahead of time.
"People are entering this country illegally, we are bringing them out legally," Trump told reporters Friday, calling it an "important operation" that will focus primarily on removing criminals.
In a typical week, ICE arrests thousands of illegal immigrants in the country, according to government data. Most of these arrests are made without prior publicity.
Since Trump first spoke of the plan, a number of city mayors, almost all Democrats, have repeated their long-standing policy of not cooperating with ICE officials on deportations and have publicized the lines assistance that people can call to understand their rights.
Democratic legislators, among others, have also tried to inform immigrants of their rights, telling them not to open their door for the ICE unless the agents present a court order, and not to say or sign anything before talking to a lawyer.
On Thursday, the American Civil Liberties Union filed a lawsuit to stop the imminent deportations, citing bureaucratic errors that the ACLU states made it impossible for people to know when their hearings took place. He said some of the interested people were not aware of being subjected to a "final removal order".
US President Donald Trump said today that mass deportation raids will begin "soon enough" as migrant defenders promised that their communities would be "ready" when immigration officers arrive.
Trump, who made the hard line an immigration issue a key issue of his presidency and his 2020 re-election, postponed the operation last month after the scheduled date was leaked to the press, but said on Monday that the raids would take place after the 4th of July holiday.
"They will start soon enough, but I do not call them raids, we are removing people, all these people who have entered illegally over the years," he told reporters at the White House on Friday.
Last month the Immigration and Customs Execution (ICE) stated that the incursions would have affected undocumented migrants who had recently arrived in the United States in order to discourage a wave of families Central Americans on the southwestern border.
The ICE said in a statement that its goal was to arrest people with criminal histories, but any immigrant found in violation of US laws was subject to arrest.
Government documents published this week by migrant rights groups showed that some incursions of the ICE had more side arrests than the apprehensions of targeted migrants. Migrant rights groups say that this general threat to undocumented migrants is detrimental to the US communities and economy, forcing adults to lose their jobs and children to skip school for fear that they be collected and separated.
"We must be ready, not only when Trump announces it, because every day there are arrests and they have increased," said Elsa Lopez, organizer of the immigrant group and labor rights of New Mexico Somos a Pueblo Unido.
Migrants' fears on the southwestern border have reached a peak of 13 years in May, but have eased in June while Mexico has increased the application of immigration.
An increasing number of migrants come from countries outside Central America, including India, Cuba and Africa. The patrol sector at the borders of Del Rio, Texas, reported the arrest of over 1,000 Haitians since 10 June.
Democratic parliamentarians visited a border patrol station in El Paso, Texas on Monday and said that migrants were held in atrocious conditions, with women who said they were drinking from a bathroom.
To "dispel" what he called "misinformation", chief border patrol officer Roy Villareal published a video showing fresh water available from a chiller and a tap in a cell of an industry migrant processing center in Tucson , in Arizona.
"We do not force foreigners to drink outside the bathroom," said Villareal, head of an area that captured about six times fewer people in May than the El Paso sector, a border section that has borne the brunt. of the impulse of migrants.