ASHINGTON, Jan. 16 — The Supreme Court agreed on Friday to decide whether foreigners who never had a legal right to enter the United States may be held indefinitely while immigration officials try to arrange their deportations.

The case presents a question raised but not directly answered by a decision by the court three years ago in a case concerning a German-born Lithuanian who entered the country legally as a child and who then compiled a long criminal record that made him deportable.

Neither Germany, Lithuania nor any other country would take the man, Kestutis Zadvydas, who remained in custody for three years before a federal judge ordered him released. The Supreme Court ruled in Mr. Zadvydas's favor, interpreting the statute governing detention before deportation to contain an implicit limitation of a "reasonable time," normally six months.

But the court observed that unlike Mr. Zadvydas, "aliens who have not yet gained initial admission to this country would present a very different question." Since then, the lower federal courts have divided over whether that different question should have a different answer.

The Bush administration urged the court to resolve the dispute, which has "great significance for the enforcement of the immigration laws, national security and public safety," Solicitor General Theodore B. Olson said in the government brief.

Mr. Olson told the court that there were more than 1,000 people in this category, immigrants who were never lawfully admitted, had been found deportable and have been in detention for more than six months. Most are Cubans who arrived in the 1980 Mariel boatlift and whose return Cuba has refused to accept.

The case that the justices accepted is an appeal filed on behalf of one of the Mariel Cubans, Daniel Benítez. Like some 125,000 other Cubans who were formally denied entry at that time, Mr. Benítez was admitted a temporary parole that did not convey the status of legal residency. While in the United States, he compiled several criminal convictions that the old Immigration and Naturalization Service determined made him ineligible for lawful permanent residency. He was placed in immigration custody in October 2001.

As his detention approached six months, he filed a habeas corpus petition, arguing that he was entitled to release under the reasoning of the Zadvydas decision. Both the Federal District Court in Panama City, Fla., and the United States Court of Appeals for the 11th Circuit, in Atlanta, held that the Zadvydas ruling applied just to "resident aliens."

His appeal, Benítez v. Mata, No. 03-7434, argues that the statute that the court interpreted in the Zadvydas case makes no distinction between resident aliens and "excludable" ones like Mr. Benítez. Two other federal appeals courts, his lawyers pointed out, have held that the statute "cannot be interpreted one way for admitted aliens and another way for nonadmitted aliens."

In any event, the appeal maintains that "it is at least a serious question whether the Constitution permits the government to lock a nonadmitted alien in prison for the rest of his life because his home country will not take him back." For that reason, it says, the court should interpret the statute as it did in the Zadvydas case, to avoid what would otherwise be a substantial issue of due process.

Justice Stephen G. Breyer's majority opinion in that case said open-ended detention would pose a "serious constitutional threat" that the court should avoid by interpreting the statute to have a reasonable time limit.

While agreeing in the new case that the question needed resolution, the administration told the justices that the 11th Circuit limitation on the Zadvydas decision was correct.