The likely Republican nominee was born on a US naval base in 1936 in the Panama Canal Zone.

A federal judge in California has been asked to determine whether McCain meets the legal test to hold the nation's highest office. Although McCain has called questions about his eligibility nonsense, his campaign, as it did in his first White House run in 2000, sought a review from legal experts to put the issue to rest.

"Based on the original meaning of the Constitution, the Framers' intentions, and subsequent legal and historical precedent, Senator McCain's birth to parents who were US citizens, serving on a US military base in the Panama Canal Zone in 1936, makes him a 'natural born citizen' within the meaning of the Constitution," the review found.

The issue was examined by former Solicitor General Ted Olson, a Republican backing McCain, and Harvard Law Professor Laurence H Tribe, a Democrat backing Barack Obama.

The Constitution requires that only "natural born" citizens hold the presidency. But the Founding Fathers did not elaborate on the term, and the meaning of the phrase has long been debated.

A two-page complaint filed March 6 in US District Court in Riverside, California, argued that a judge should step in because the constitutional language was not precise, opening questions about McCain's standing. It was filed by Riverside lawyer Andrew Aames, who says he's a registered Republican but previously was a Democrat.