The Obama administration has hit out at Russia's decision to supply Syria with anti-ship missiles.
General Martin Dempsey, chairman of the Joint Chiefs of Staff, said the move was "ill-timed and very unfortunate" and will only worsen the civil war, AP reported.
Dempsey said the missile delivery would embolden Syrian President Bashar Assad's regime and "prolong the suffering".
He was commenting on a New York Times report that Russia has sent advanced antiship cruise missiles to Syria.
The New York Times quoted an unnamed military source saying that while Russia has previously supplied weapons to Syria, the latest round are more sophisticated in countering any potential future foreign military intervention in Syria.
The source said the move is a clear indication of the depth of Russia's support for the Syrian government led by President Bashar al-Assad.
GlobalPost senior correspondent Noga Tarnopolsky said that the weapons Russia sent to Syria are "likely to interfere with any of the non-lethal international efforts that have been discussed as possibilities: a no-fly zone, a naval blockade, the transfer of materiel to the rebels."
As such, "Russians seem to be pushing the Western powers into a corner," Tarnopolsky said. "If Russia succeeds, that would leave Europe and the United States with only two options: do nothing, or enter with overwhelming, massive military force and be prepared to confront extremely advanced Russian weapons systems."
Russia's foreign minister would not confirm details but said Russian supplies did not break any international rules, the BBC reported.
Foreign Minister Sergei Lavrov said Friday he did not understand the uproar sparked by Moscow's continuing weapons cooperation with Syria.
"I do not understand why the media is trying to create a sensation out of this," Lavrov said, according to Agence France-Presse.
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During a joint press appearance in Sochi with visiting United Nations Secretary General Ban Ki-moon, Lavrov said: "We are first and foremost supplying defense weapons related to air defense.”
"We have not hidden that we supply weapons to Syria under signed contracts, without violating any international agreements, or our own legislation."
GlobalPost's Tarnopolsky said that "in fact, these anti-missile systems are equipped with significantly more sophisticated systems than anything Assad has gotten before."
Moreover, sending the missiles as well as warships the very week Putin held diplomatic meetings with both the United States and Israel on the subject of Syria — and while the United States is pushing for a Russian-US led summit in early June — "shows a really breathtaking lack of consideration for Western concerns, " Tarnopolsky added, "and for the niceties of normal diplomatic discourse."
Stephen Sestanovich of the Council on Foreign Relations told GlobalPost via email that, "Russia stubbornly defends its right to support other sovereign states to defend themselves. For them, this is a matter of dollars and cents but also high principle."
"The standard Russian response to criticism of such moves is that they're simply fulfilling a contract that's been in place for years. They'll say that it doesn't matter that Syria has become a war zone since the contract was signed," Sestanovich said.
Lavrov has urged that a peace conference bringing the Syrian government and opposition to the negotiating table should be held as soon as possible.
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Does the delivery of the missiles contradict Russia's push for a peace conference? Sestanovich observed: "The Russian answer would be that they'll have more influence over the Syrian government by not abandoning them."
"The same logic would suggest that the US and its allies would have more influence over the insurgents by giving them arms," Sestanovich said. "The Russians would denounce that idea, but they are probably making it more likely that this will happen."
To date, the West's support for the Syrian opposition has been of the non-lethal and humanitarian variety. US President Barack Obama stressed the importance of maintaining pressure on the Assad regime while meeting with British Prime Minister David Cameron Monday.
Cameron, who met with Putin last week, said, "It is in both our [Russia and Britain's] interests that at the end of this there is a stable Syria."
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The reports of Russia's support for Syria's military come amid growing alarm that chemical weapons may be being used in Syria.
Last month, Obama said there was evidence chemical weapons were used, but there was still much that US intelligence agencies did not know, Reuters reported.
"We don't know how they were used, when they were used, who used them," he said, and, "We don't have a chain of custody that establishes what exactly happened," he told a White House news conference.
Obama has not ruled out military action against Assad's government, but while speaking at a press conference with Turkish Prime Minister Reccep Tayyip Erdogan on Thursday, he ruled out acting unilaterally.
As for the missiles, Sestanovich said, "We don't know a lot about what these missiles can do. For a long time, Western analysts have explained that the Russian-supplied air defense system that Syria has is extremely effective. Then Israel bombed military sites in Syria, and Syrian air-defenses looked completely useless."
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