PITTSBURGH (AP) - Cindy McCain's jab to her husband's back came a second too late Tuesday to keep him from making a wisecrack about the health impact of Iran's main import from the United States: cigarettes.

Republican presidential candidate John McCain was asked about an Associated Press report that $158 million in cigarettes have been shipped to Iran during George W. Bush's presidency despite restrictions on U.S. exports to that country.

"Maybe that's a way of killing them," McCain told reporters, smiling as he waited for a cheesesteak sandwich at the Primanti Brothers restaurant. His wife, sitting next to him at the counter, poked his back without looking up.

"I meant that as a joke," McCain quickly explained. "As a person who hasn't had a cigarette in 28 years," he began to say, when his wife corrected him: 29 years.

Taking a more serious tone, McCain said, "I'd like to look into" details of exports to Iran. "This is the first that I've heard about it," he said.

Compiled by Charles Babington.