George W Bush has called for a major overhaul of US law to give legal status to millions of illegal workers.
More than 60% of illegal workers in the US are Mexican
The plan would allow some of America's undocumented immigrants - at least eight million, 60% Mexican - to work legally in the US for a fixed period.
Many see the plan as a bid by President Bush for the Hispanic vote in this year's presidential election.
"He wants their sweat and labour, but he ultimately doesn't want them," said New Jersey Democrat Bob Menendez.
The programme would not offer workers permanent residency or citizenship.
Allows estimated 8m illegal immigrant workers chance to work legally in the country for a fixed period
Will gain legal status for an initial period of three years if can prove they have jobs
Will be able to travel freely between US and their home countries
Workers can apply for guest worker status at a US company if it is proved no US citizen can take the job
Can apply for green card giving permanent residency in US, although Mr Bush said there would be no special preference for such workers
"[The programme] rewards business over immigrants by providing them with a permanent pool of disenfranchised
temporary workers who could easily be exploited" Democratic presidential hopeful Senator John Kerry said.
Also running for the Democratic nomination, Senator Joseph Lieberman said the president had made "an election-year conversion".
Mr Bush has also come under fire from within his own party over the scheme.
"I'm not for allowing illegals to stay in this country. I think they should have to go back... and get in line... and apply for a guest worker position," Republican representative Virgil Goode of Virginia said.
But the measures have been welcomed by some American businesses and by
Mexican President Vicente Fox who said the plan recognises "the value of the Mexican men and women who find themselves working in the US."
President Bush said America needed an immigration policy that "reflects the American dream".
Tensions over illegal immigrants run high in some communities
"As a nation that values immigrants and depends on
immigrants, we should have immigration laws that work and
make us proud."
But that was not the case, the president said.
"Instead we see many employers turning to the illegal labour market. We see millions of hard-working working men and
women condemned to fear and insecurity in a massive
The president argued that a more rational and more humane immigration law will make Americans safer as the government will have a better idea of who is crossing US borders.
"America must control its borders. This duty has become more urgent since 11 September," the president said, outlining the measures taken so far to step up security at ports of entry to the US.
1.5m illegal immigrants are repatriated
1,224 die attempting to reach the US, of whom:
400 die of thirst in the desert
300 drown in the Rio Grande
He also stressed that the proposals would not offer a blanket amnesty for people in the US illegally.
The US Chamber of Commerce, which represents three million businesses, has been lobbying for the proposed measures.
"We have 10.5 million illegal workers in the United States right now," according to US Chamber of Commerce President Thomas Donohue.
Caution and criticism
President Bush entered office in 2000 pledging to reform immigration policy, but the issue was put on hold following the 11 September 2001 attacks.
Some Hispanic groups remain cautious, however.
"We really want to see some sincere policy outcomes and see something that really helps the immigrant community and not just the Bush campaign," said Michele Waslin of the National Council of La Raza.
Those working in the field of immigration law also expressed doubts.
"The hype and misinformation that this speech will fuel in
the immigrant community will be huge. Unfortunately, the
excitement will far outweigh the real effect," Jeff Goldman, an immigration lawyer with Boston law firm Testa, Hurwitz and Thibeault told Reuters.