JERUSALEM, Dec. 20 (Xinhua) -- Israeli Prime Minister Benjamin Netanyahu warned Thursday that Israel will increase its actions against Iran's efforts to establish a military foothold in Syria, a day after the United States said it started to pull out from Syria.

"We will continue to act very aggressively against Iran's attempts to establish itself in Syria," Netanyahu said during a trilateral summit with his Greek and Cypriot counterparts in Israel.

Netanyahu said that Israel will not accept Iranian forces on the territory of its northern neighbor.

He added that Israel has the backing of the White House in its actions against the Islamic republic of Iran.

The remarks came a day after U.S. President Donald Trump said in a video on Twitter that the U.S. had defeated the Islamic State and started to withdraw its forces from the war-torn country.

The move was widely criticized in Israel and seen as an embarrassment to Netanyahu's foreign policy, in which his close relationship with Trump plays a central role.

Yair Lapid, leader of the opposition Yesh Atid party and Israel's former finance minister, tweeted "the surrender of the Americans from Syria is a failure of Netanyahu's foreign policy. It clears the way for Iran's expansion and narrows Israel's ability to bargain with the Russians."

Ehud Barak, Israel's former prime minister, said the move exposed Netanyahu's dependence on his ties with the U.S. and Russian leaders.

"Trump is deserting Syria and the Iranians are celebrating," Barak tweeted, saying that "only Israel is responsible for its own future and fate."

Netanyahu said in a video statement on Wednesday that Israel needs to study the decision, noting that the White House had told him in advance about Trump's intention to withdraw forces from Syria.

"They made it clear that they have other ways of expressing their influence in the area," he said.

Israel and Syria share a disputed border in the Golan Heights, which Israel seized in the 1967 Middle East war and annexed in a move never recognized internationally.

The Israeli military has carried out dozens of air attacks in recent years against Iranian and Syrian army positions in Syria, in addition to weapons convoyed for Hezbollah, a Lebanese Shiite militia.

Israel and the United States charge Iran's presence in Syria as a threat to Israel.