Russia announced Monday that the Syrian government will be supplied with S-300 missile defense systems amid the downing of a Russian plane by Syria last week, a move the Trump administration calls a “major mistake.”

The transfer of advance missile systems comes after a friendly fire incident between Syrian and Russian forces that led to the deaths of 15 Russians on board on a Russian military aircraft. The Kremlin initially blamed Israel, which reportedly carried out over 200 strikes on Iranian-linked targets in Syria.

The Trump administration urged Russia to reconsider the move, warning that that supplying Syria with an advanced missile defense system would be a “major mistake” and “significant escalation”.

U.S. National security adviser John Bolton said on Monday: "We have American forces in the area we're concerned about.

"The Israelis have a legitimate right to self-defense against this Iranian aggressive behavior, and what we're all trying to do is reduce tensions, reduce the possibility of major new hostilities. That's why the president has spoken to this issue and why we would regard introducing the S300 as a major mistake."

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Russian officials said that the current S-200 systems used by Syria are not sophisticated enough to identify Russian aircraft as friendly.

Vladimir Putin, the Russian president, accepted that the downing of a Russian jet was a case of friendly fire, blaming a “chain of tragic, fatal circumstances”. But Sergei Shoigu, his defense minister, put the blame on Israel for putting the Russian crew at risk.

“The Israeli crews, who knew perfectly well the situation in the air, found cover behind the Russian airplane, which led to its destruction and the deaths of 15 members of the service,” the defense minister said on Monday. “This compelled us to take reasonable measures in response, intended to improve the safety of Russian soldiers.”

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He added that Russia will go ahead with the shipment of the advanced missile systems because “the situation has changed, and it's not our fault,” noting the supply of S-300 will “calm down some hotheads” who threaten Russian military in the Middle East.

Israel pushed back against accusations leveled against their pilots, claiming their jets were already in Israeli airspace before the Syrian missile was fired.

Prime Minister Benjamin Netanyahu told Putin on Monday that “transferring advanced weapons systems into irresponsible hands will increase the dangers in the region.”

He reiterated that Israel won’t be deterred from continuing to “defend its security and its interests” and will keep attacking Iranian-affiliated targets in Syria.

Russian Deputy Foreign Minister Mikhail Bogdanov reportedly told Russia news media that the government’s decision to supply S-300 is the country’s “own right” and said the transfer won’t hurt its relationship with Israel.

The Associated Press contributed to this report.