But they also said the 9th Circuit court in San Francisco should be given "additional time for reflection" to correct its mistake and uphold the constitutionality of the cross.
The administration's position, sent to the court this week, means the high court will likely have to decide the fate of the San Diego cross, but not this year.
The cross atop Mount Soledad was erected in 1954, but it has been under legal attack since 1989. A decade ago,
But several vets, including the Jewish War Veterans of the United States, sued, contending the Christian cross was a religious symbol.
The 9th Circuit agreed, and last year U.S. District Judge Larry Burns ruled the cross must come down. But he also put his ruling on hold while the government appeals.
Recently, several groups urged the Supreme Court to allow them to skip the 9th Circuit appeal. The high court has rejected similar requests in the past to intervene in the matter.
U.S. Solicitor General Donald Verrilli Jr. advised against this procedural shortcut, noting there is no great urgency because the judge put his ruling on hold.
But he added the 9th Circuit's earlier ruling was "wrong" and needs to be overturned, either by the appeals court or by the Supreme Court.
"The United States remains fully committed to preserving the Mount Soledad cross as an appropriate memorial to our nation's veterans," he said.
The court is expected this spring to decide an important religion case testing whether city councils may open their meetings with mostly Christian prayers. A U.S. appeals court ruled the city of Greece, N.Y., violated the ban on an "establishment" of religion by regularly inviting Christian clerics to deliver opening prayers.
Verrilli filed a brief that urged the court to reverse that ruling and uphold the city's policy.