TEL AVIV: Differences between American President Barack Obama and Israeli Prime Minister Benjamin Netanyahu over setting a “red line” for Iran’s nuclear project were never a joking matter.

Until now, when both leaders uncorked some rapid-fire one-liners during Obama’s tour of a partially U.S.-funded anti-missile system that he inspected after a red carpet welcome ceremony Wednesday at Tel Aviv airport.

“Where do you want to start?” Obama asked an Israeli military official, in a comment picked up by TV cameras providing close coverage of the president and Netanyahu walking together toward the battery.

“We are following the red line, sir,” the officer replied matter-of-factly, referring to a red line painted on the tarmac that led to the missiles.

“The red line, OK,” said Obama, who smiled, gestured with his thumb toward Netanyahu and said: “He’s always talking to me about red lines.”

It was a rare moment of levity between the two, whose often-testy relationship has been illustrated by stern-faced appearances before cameras during Netanyahu’s visits to the White House.

The public display of bonhomie lightened the tone at the start of a visit by the U.S. president that is not expected to produce much in the way of policy initiatives.

In a speech at the United Nations in September, Netanyahu drew a red line on a cartoonish drawing of a bomb, depicting the point where he said Iran would have enough medium-enriched uranium to move rapidly toward building a nuclear bomb.

Continuing his banter as he walked along the thin red line at the airport, Obama said with a smile: “So this is all a psychological ploy.”

Chuckling, Netanyahu shot back: “This was minutely planned.”

Obama also joked with some Israeli military officials as he hopped out of an SUV on the tarmac, and said: “I’m a young man. I’m always looking for a chance to walk.”