On day one of his trip to the Middle East, U.S. President Barack Obama met with Israeli Prime Minister Benjamin Netanyahu in Jerusalem -- offering tough talk on a wide range of regional issues.

At a joint news conference, Obama said the U.S. was investigating alleged chemical weapons use Syria, and maintained he would hold the Assad regime accountable.

(SOUNDBITE) (English) U.S. PRESIDENT BARACK OBAMA, SAYING:

"We have been clear that the use of chemical weapons against the Syrian people would be a serious and tragic mistake."

On Iran, Obama said diplomacy is the first option, but added:

(SOUNDBITE) (English) U.S. PRESIDENT BARACK OBAMA, SAYING:

"All options are on the table. We will do what is necessary to prevent Iran from getting the world's worst weapons."

Netanyahu -- meanwhile -- hinted at a possible go-it-alone plan to attack Iran's nuclear program.

(SOUNDBITE) (English) ISRAELI PRIME MINISTER BENJAMIN NETANYAHU, SAYING:

"Tha