JERUSALEM - Israel announced Sunday that it was constructing a border fence along the length of its armistice line with Syria in the Golan Heights and was coordinating its intelligence with the United States in light of the deteriorating security situation in Syria.

In remarks at the start of the weekly Cabinet meeting, Prime Minister Benjamin Netanyahu said the Syrian army had moved away from the frontier and that jihadist forces had moved in.

"Therefore, we will defend this border against both infiltration and terrorism," Netanyahu said, adding, "I also submit to the Cabinet the fact that the Syrian regime is very unstable, that the question of chemical weapons here worries us." He said that Israel was coordinating with the United States and others "so that we might be prepared for any scenario."

Netanyahu's announcement came as he sought to reinforce his security credentials before elections on Jan. 22, and as he appealed to his traditional supporters to cast their ballots for the conservative Likud-Beiteinu ticket he is leading and not be lulled by polls showing that he is favored to prevail.

Israel has largely stayed out of the fighting in Syria, but in recent months a number of stray mortar shells crashed into the Israeli-controlled territory as Syrian government forces battled rebels across the line, prompting Israel to fire warning shots into Syria and in one instance aim tank fire at a Syrian position.

But apprehension has been mounting, with Israeli experts warning that Syria is becoming a haven for extremists.

NEW YORK TIMES