The Department of Homeland Security (DHS) said the crackdown would aim to ''reverse the tolerance of illegal employment and illegal immigration in the US.''

Underlining the new policy, DHS said seven managers of a nationwide company that employed hundreds of illegal immigrants had been arrested. Searches of 40 of the company's plants also resulted in the arrest of 1,187 illegal immigrants.

DHS identified the company as IFCO Systems North America Inc, based in Houston, Texas.

''Employers and workers alike should be on notice that the status quo has changed,'' DHS secretary Michael Chertoff said.

The initiative aims to complement border security in the interior of the US. It was unveiled amid a heated debate among politicians and ordinary Americans over immigration reform.

Some members of Congress want a tough immigration policy that makes illegally crossing the US border a felony, which could result in millions of immigrants being deported.

An alternative plan would allow most of the estimated 11 million illegal immigrants to be put on a path to citizenship after paying fines and back taxes as well as fulfilling other requirements.

DHS wants to target employers who ''knowingly or recklessly hire unauthorized workers ... often because they know that those are the workers who can't complain when they're exploited or injured on the job,'' he added.

As part of the plan, the US will seek to remove jailed and fugitive foreign-born nationals, and also target and remove those who have overstayed their visas or pose a security threat, DHS said.

The government also said it aims to dismantle human smuggling organizations that bring illegals into the country and to punish people who commit immigration-related document fraud.