Homeland Security Secretary John Kelly told a news conference in Guatemala, after talks with that country's president: "We are not going out and doing mass deportations."
He said that two memos he signed Tuesday, enacting directions from US President Donald Trump to clamp down on immigrants deemed to be in the United States illegally would prioritise "criminal offenders" while ensuring due process in US courts was upheld.
"But there will be no mass roundups. When we do take someone into custody they are then put into the American legal justice system -- that's the courts, and it's the courts that will decide what happens to them," he said.
Kelly's visit to Guatemala -- one of three violence- and poverty-wracked Central American countries that provide many undocumented migrants to the US -- was the first by a senior US official since Trump took power last month.
Guatemala, El Salvador and Honduras are especially concerned about Trump's drive to cut down on illegal immigration and to reduce the size of the undocumented migrant population in the US, estimated at 11 million.
Many of those living in America provide a vital financial lifeline to family in Latin American countries in the form of remittances.
Migration conference
Guatemala's interior minister, Francisco Rivas, said Kelly discussed migration and the scourge of violent gangs with his president, Jimmy Morales.
Rivas also said preparations were under way for a migration conference at which Guatemala, El Salvador and Honduras would be represented. It could take place in Mexico or the United States, he said.
Kelly said that Trump's executive order meant a boost in the number of US border patrol officers and the construction of a "physical barrier" -- the wall Trump has repeatedly vowed to have built along the entire border with Mexico.
The Department of Homeland Security was therefore now working on "the expansion of expedited removal operations, prioritising criminal prosecutions for immigration offenses committed at the border, and empowering state and local enforcement agencies to assist in enforcing immigration laws," Kelly said.
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He offered "sincere advice" to any Guatemalans thinking of paying people smugglers to try to get them illegally into the United States "to not do it."
The journey was very dangerous, "and the very, very considerable money you will have to pay the 'coyotes' (people smugglers) will be lost because we are picking up, that is to say reinforcing, our turnback efforts on the border."
He added that, "by law, we are required to return irregular migrants to their home country."
Kelly did not address US plans to have deported Central Americans sent to Mexico -- something Mexico has signaled it may not accept.
On Thursday, Kelly and Trump's secretary of state, Rex Tillerson, were to meet with Mexican President Enrique Pena Nieto.
Trump has angered Mexico by vowing to build the wall to keep out migrants from Latin America and revise trade relations. During his election campaign, Trump branded some immigrants from Mexico as rapists and criminals.
