Republican Senator Lindsey Graham doubled down on his unusual warning to Israel on Thursday about any attempts to reach an agreement with Russia over the situation in Syria, saying it could potentially affect U.S. national security interests.

Responding to a Haaretz.com tweet quoting Netanyahu saying that Israel doesn't have a problem with the Assad regime, Graham tweeted: "Just to be clear: Without Iran/Hezbollah, Syria's Assad would not be in power and would not have the ability to slaughter almost a half-million Syrians. Without Assad’s blessing, the flags of Hezbollah and the Iranian Revolutionary Guard would not be on Israel’s front door."

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Earlier, Graham took to his official Twitter account to send the message that trusting Russia would be a mistake for Israel. When asked about Graham's earlier tweet, Netanyahu said that Israel acts with full transparency with the United States. He added that he agrees with Graham that Israel should act against Iran's presence in Syria.

"To our friends in Israel – be very careful making agreements with Russia re Syria that affect U.S. interests," Graham wrote, adding "I don’t trust Russia to police Iran or anyone else in Syria. U.S. must maintain presence in Syria to ensure ISIS doesn’t come back and to counter Russia/Iran influence."

When asked about Graham's earlier tweet, Netanyahu said that Israel acts with full transparency with the United States. He added that he agrees with Graham that Israel should act against Iran's presence in Syria.

Graham's tweet came ahead of Netanyahu's meeting with President Vladimir Putin in Russia to discuss the situation in Syria amid reports about an Israeli proposal in which Russia would push Iran out of Syria, and in return the United States would lift sanctions on Russia and accept its invasion of eastern Ukraine. The New Yorker reported this week that such a proposal was made by Israeli officials in early 2017, during the transition period between the Obama and Trump administrations.

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Graham is considered a hawkish voice in Syria in the Senate, and also a strong supporter of the Israeli government, which makes his public warning to Israel unusual. In a subsequent tweet, he added that an American withdrawal from Syria would be a "disaster" for American interests and allies, including the Kurds in Syria and Iraq.

Graham's statement could point to unease in Washington around the increase coordination between Israel and Russia in the Syrian arena, and the possibility that such coordination is diminishing the United States' role. Prime Minister Netanyahu has pointed out numerous times in recent months that Israel is closely coordinating its positions regarding Syria with the Trump administration, at the same time that Israel is trying to reach an understanding with Russia.