The Middle East, where Obama encounters red lines at every turn

US president Barack Obama arrives with Palestinian counterpart Mahmoud Abbas at a joint news conference in the West Bank city of Ramallah.

JERUSALEM // Red lines.

When it comes to the Middle East, the US president, Barack Obama, is encountering them everywhere. They are painted on the ground as directional markers for visiting dignitaries, and they are in Mr Obama's and Israeli prime minister Benjamin Netanyahu's foreign policy rhetoric as not-to-be-crossed warnings to Syria and Iran.

As Mr Obama prepared to tour a missile battery that is part of Israel's Iron Dome defences, an aide at the Tel Aviv airport directed the president to follow the red line on the tarmac.

"Bibi's always talking to me about red lines," Mr Obama quipped, referring to Mr Netanyahu by his familiar name.

The Israeli premier has set "red lines" on Iran's nuclear development capabilities. Israel repeatedly has threatened to take military action should Iran appear to be on the verge of obtaining a bomb. The US has pushed for more time to allow diplomacy and economic penalties to run their course, though Mr Obama insists military action is an option. The issue has become a point of tension between the two allies.

Mr Obama himself has used the phrase to describe limits that could prompt action against Bashar Al Assad regime. Any use of chemical weapons by Syria's regime, Mr Obama has said, would constitute a "red line" that if breached could prompt direct US intervention. It is a threat that could be tested amid new accusations this week that the regime used chemicals in an attack in a village in the north of Syria.

Referring to the painted red lines at the airport, Mr Obama joked that it was "a psychological ploy".

Mr Netanyahu replied: "It was minutely planned."

The US president's travelling retinue is no small matter. The combination of aides and press who follow the president makes for a massive grouping of followers that are simply part of the job of being president. But if Mr Obama does not take notice, someone else in his family certainly does.

"Michelle teases me mercilessly," Mr Obama confessed to Mr Netanyahu, referring to his entourage during arrival ceremonies in Tel Aviv. "She says whenever she travels with me, it's embarrassing."

The Israeli president, Shimon Peres, presented Mr Obama with gifts during their meeting. Mr Obama received a friendship clock, which has the time in Washington on one side and the time in Jerusalem on the other, and a gold inscription of the US presidential seal. The clock was made at Adi Watches in Kibbutz Yavne, the only watch factory in the Middle East.

Mr Peres also gave the president a friendship bracelet for the first lady. It is designed as two circles, representing the two nations, with a small freedom bird on each. Mr Obama's daughters also are being sent bracelets with freedom birds.

Israelis and others awaiting Mr Obama's arrival in Israel on Wednesday were surprised to see his signature black limousine sitting on the back of a flatbed lorry.

The US secret service said the vehicle suffered mechanical problems before Mr Obama arrived but wouldn't say just what the problem was. Mechanics were examining the vehicle to figure out what happened.

The disabled limo was swapped out for a backup, and Mr Obama's busy itinerary in Tel Aviv and Jerusalem on Wednesday was unaffected. The secret service says its advance teams plan ahead for these types of glitches.

"This is why we bring multiple vehicles and a mechanic on all trips," said the secret service spokesman, Brian Leary.