US President George W Bush has called for the debate over a controversial new immigration bill to be conducted in a "civil and dignified way".
George W Bush told the new US citizens it was a "joyful day"
He told a naturalisation ceremony that immigrants "shaped America's identity" and were vital to the economy.
In its first step to full legislation, the bill has been passed by the Senate Judiciary Committee and now goes to the full Senate on Tuesday for debate.
The bill has been attacked by both conservatives and pro-immigrant groups.
President Bush's Republican Party is divided over his plans to create a guest-worker scheme allowing foreigners to stay for a set time in specific jobs.
Meanwhile, thousands have taken to the streets across the US in protest at plans within the bill to criminalise illegal workers.
Swearing in new US citizens at the naturalisation event in Washington, Mr Bush urged all sides of the debate to tone down their rhetoric.
He said securing borders was a top priority but he also invoked the country's history as "a nation of immigrants" to argue for a balanced approach.
He argued that a guest-worker programme would provide a legal way of matching immigrant workers with employers, giving them jobs that Americans did not want.
Workers should be able to register for legal status on a temporary basis, he said, adding they would have to "get in line" if they decided to apply for citizenship.
"This programme would help meet the demands of a growing economy, and it would allow honest workers to provide for their families while respecting the law."
But he said the programme would not mean those already working illegally in the US would be allowed to stay.
"I believe granting amnesty would be unfair, because it would allow people who break the law to jump ahead of you all... people who play by the rules and have waited in line for citizenship."
Mr Bush said it was important the Congress passed the comprehensive immigration bill.
The president congratulated the new US citizens, wishing them luck as "citizens of the greatest nation on the face of the Earth".
Key election issue
The House of Representatives passed an immigration bill last December, which included tough enforcement measures but excluded any guest work provision.
Immigrants are said to do many of the jobs Americans do not want to
Activists opposed to tougher immigration laws took to the streets again on Monday, with protests held in a number of cities including one outside the Capitol building in Washington.
About half a million people rallied in Los Angeles, California, at the weekend.
The immigration bill would also impose new penalties on employers who hire illegal immigrants and allow for the erecting of fences along a third of the US-Mexican border.
The proposals have angered many Hispanic-Americans, a key voting bloc in November's mid-term elections.
It is estimated that 11.5 million people are living in the US illegally. Many of them work in the agricultural sector and the construction and service industries.