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.