WASHINGTON — Conservative legislators from five states opened a national campaign on Wednesday to end the automatic granting of American citizenship to children born in the United States of illegal immigrants.

At a news conference here timed to coincide with the start of a new Congress, Republican state lawmakers introduced two model measures curtailing citizenship rights for children of illegal immigrants. The legislators said the measures would be introduced in at least 14 states.

They acknowledged that the state bills were not likely to have a practical effect anytime soon, since they will quickly be challenged as unconstitutional. But the legislators — from Arizona, Georgia, Oklahoma, Pennsylvania and South Carolina — said they chose the first day of a new Republican-controlled House of Representatives to start an effort that they hope will end with a Supreme Court decision on birthright citizenship, and spur legislative action in Washington.

In a separate effort, Representative Steve King of Iowa, a Republican who will be chairman of the House Judiciary subcommittee on immigration, said Wednesday that as soon as the new House members were sworn in, he would introduce a bill to eliminate birthright citizenship for children when both parents were illegal immigrants.

But it was the state lawmakers’ initiative that moved the highly emotional issue of birthright citizenship, which had long been marginal in the immigration debate, to the front of the Republicans’ immigration agenda in the 112th Congress.

“We are here to send a very public message to Congress,” said Daryl Metcalfe, a Republican state representative from Pennsylvania. “We want to bring an end to the illegal alien invasion that is having such a negative impact on our states.”

The states’ campaign brought an outcry from immigrant, Latino and African-American civil rights organizations. Several of them announced they had formed a coalition to bring court challenges to any birthright citizenship laws that passed state legislatures.

“For the first time since the end of the Civil War, these legislators want to pass state laws that would create two tiers of citizens, a modern-day caste system,” said Wade Henderson, president of the Leadership Conference on Human and Civil Rights, which includes many African-American groups.

His group is in the new coalition, along with the National Association for the Advancement of Colored People and the National Council of La Raza, among others.

The lawmakers were challenged even before they finished speaking. The news conference, held at the National Press Club, was interrupted four times by protesters who stood one by one to brandish posters and accuse the lawmakers of intolerance and racism. One protester cited welcoming words for immigrants inscribed at the site of the Statue of Liberty.

A brief scuffle erupted when a man who was a supporter of the state initiatives seized one protester by the arm and tried to march him out of the room. Also present were supporters of the lawmakers, who clapped and cheered.

One model measure the lawmakers presented was a bill creating a new definition of state citizenship, in addition to national citizenship, which would exclude babies born in the state with two illegal immigrant parents.

The second measure was a compact between states, in which they would agree to issue distinctive birth certificates to babies whose parents could not show legal immigration status.

The state bills would also deny citizenship to newborn children of hundreds of thousands of legal immigrants who live in the United States on temporary visas.

The right to United States citizenship for everyone born on American soil is described in the 14th Amendment. The state legislators argued that one phrase in the amendment — which guarantees citizenship to everyone born or naturalized in this country “and subject to the jurisdiction thereof” — signals that it was not intended to apply to children of immigrants who do not have lawful status.

The 14th Amendment was adopted in the wake of the Civil War to guarantee citizenship to the American-born children of freed slaves. In the debate on Wednesday, there were frequent references to the Civil War.

Daniel B. Verdin, a senior Republican state senator from South Carolina, called illegal immigration “a malady of epic proportions,” which he said compared with “the malady of slavery.”

The state lawmakers said illegal immigrants had a dire effect on state budgets. Mr. Metcalfe said that Pennsylvania was facing “nothing less than an invasion,” and that Congress had a constitutional responsibility to protect states from foreign invasion.

Kris Kobach, a constitutional lawyer who was recently elected secretary of state of Kansas, said the proposed laws were carefully written to avoid usurping federal authority, but to “revive the concept of state citizenship.”

But opponents of the proposals said that determining American citizenship was clearly a federal matter in which states had no legal role.

“We believe these laws cannot survive constitutional scrutiny,” said Lucas Guttentag, director of the immigrants’ rights project of the American Civil Liberties Union, another group in the new coalition.

Mr. King, the Iowa congressman, said the birthright citizenship bill he would introduce might not be his first priority for passage. He said he would focus first on legislation to crack down on employers who hire unauthorized immigrant workers.

Several House lawmakers said Mr. King’s citizenship bill could pass, although it was likely to be defeated in the Senate, where Democrats hold a majority.

“I would have said a year ago that Republicans would not embrace anything so drastic,” said Representative Charlie Gonzalez, a Texas Democrat who is chairman of the Congressional Hispanic Caucus. “But anything is possible now.”

Some Latino Republicans expressed dismay that the party was making birthright citizenship a central element of its immigration policy.

“Rather than attacking babies born in the United States and the Constitution, we demand they target our suffering economy,” said Deedee Garcia Blase, a spokeswoman for Somos Republicans, a Texas-based organization of Latino Republicans.

Copyright 2011 The New York Times Company. Reprinted from The New York Times, National, of Thursday, January 6, 2011.