President Obama in his first visit to Israel as commander in chief said his administration will investigate whether Syria’s government used chemical weapons against rebels in its civil war.

The question of whether Syria had crossed a so-called “red line” that would provoke U.S. military action dominated the president’s first day in Israel, which included a meeting and joint press conference with Israeli Prime Minister Benjamin Netanyahu.

Obama offered a generally cautious approach, saying facts needed to be gathered but reiterating his past statement that the use of chemical weapons could lead to new actions by the United States.

“I have made clear that the use of chemical weapons is a game-changer,” Obama said as Netanyahu looked on. “And I won’t make an announcement today about next steps because I think we have to gather the facts.”