Republican Cruz pushes back on questions about his U.S. citizenship

MASON CITY, Iowa (Reuters) - Republican presidential hopeful Ted Cruz on Friday defended his American citizenship at a campaign stop in Iowa, pushing back against questions raised by rival Donald Trump, who suggested Cruz's Canadian birthplace might complicate his White House bid.

"I've never been naturalized," said Cruz, the U.S. senator from Texas who is among the front-runners for the party's nomination. "It was the process of being born that made me a U.S. citizen."

Cruz is a U.S. citizen by birth because his mother was American, although he was born in Canada.

As Cruz has pulled ahead of the Republican pack in the key early-voting state of Iowa, businessman Donald Trump, who leads Republicans nationally, has stepped up aggressively questioning whether Cruz is a natural-born citizen and calling the senator's Canadian birth a potential problem for the party.

Cruz spoke at Praise Community Church in Mason City, Iowa, where he is on the fifth day of a six-day bus tour across the state.

Presidents must be "natural-born citizens" under the U.S. Constitution. Cruz was born in Calgary, Alberta, but his mother was a U.S. citizen, which he says meets the requirements to run.

"The child of a U.S. citizen born abroad is a natural-born citizen," Cruz said.

"As a legal matter the question is quite straightforward," he added.

Cruz cited other similar examples, including Senator John McCain. In the 2008 presidential race, McCain, the Republican nominee, had faced questions on his citizenship because he was born, to American parents, on a military base in the Panama Canal Zone, which was then under U.S. control.

(Reporting by Luciana Lopez; Editing by Leslie Adler)