Prime Minister Benjamin Netanyahu told Russian President Vladimir Putin at a meeting in Moscow on Thursday that the Golan Heights must remain a part of Israel and is a "red line".

Netanyahu arrived in Moscow on Thursday to discuss closer military coordination to avoid incidents between Israel and Russia, which launched a military operation in support of Syrian President Bashar Assad last year. The meeting is also attended by Immigrant Absorption Minister Zeev Elkin, Israel Air Force chief Amir Eshel and acting National Security Council head Jacob Nagel.

"We are doing everything to prevent the emergence of an additional front of terror against us at the Golan Heights," Netanyahu said at the start of the meeting.

Netanyahu has expressed concern to Russia's president that sophisticated weapons from Syria and Iraq could end up in the hands of the Lebanese militant group Hezbollah, a close ally of the Syrian government.

Netanyahu said Israel will insist on its red lines, either the transfer of weaponry from Iran and Syria to Hezbollah or the opening of a front against Israel in the Golan Heights.

"These are [our] red lines, and we will continue to ensure" that they are not crossed, Netanyahu said. "With an agreement or without an agreement, the Golan Heights will remain under Israeli sovereignty."

A senior commander said that "Israel isn't concerned that Russia will assume an active role in the attempt to return the Golan Heights to Syrian hands. The main fear is that Russia will agree to such requests which have already been brought to the negotiations table by the Syrian side."

U.S. State Department spokesperson John Kirby stressed Monday night that the Obama administration does not consider the Golan Heights to be part of Israel, a day after Netanyahu vowed they "will forever remain under Israeli sovereignty."

"The U.S. position on the issue is unchanged," Kirby told reporters during a daily briefing at the State Department in Washington. "This position was maintained by both Democratic and Republican administrations. Those territories are not part of Israel and the status of those territories should be determined through negotiations. The current situation in Syria does not allow this," Kirby added.

Israel captured the Golan from Syria in the 1967 Six Day War and annexed it in 1981.