WASHINGTON — Secretary of State John Kerry on Friday strongly criticized Russia’s pledge to send advanced antiaircraft weapons to Syria, saying that its actions threatened to disrupt efforts to negotiate a political settlement of the Syrian conflict and posed an unacceptable risk to Israel.
“Whether it’s an old contract or not, it has a profoundly negative impact on the balance of interests and the stability of the region, and it does put Israel at risk,” Kerry said at the State Department, making his most pointed statement yet about Russia’s arming of the government of President Bashar Assad.
Russia’s announcement last week that it would go ahead with the sale of S-300 missiles to Syria — and Assad’s boasts Thursday about the durability of his Russian weapons supply — have added a dangerous new dimension to the civil war, even as Kerry and his Russian counterpart, Sergey V. Lavrov, have worked to hold an international conference in hopes of finding a way to end the fighting.
Kerry, who appeared with Germany’s foreign minister, Guido Westerwelle, suggested Russia’s continued sale of sophisticated weaponry to Assad’s government called into question its commitment to the political process that he and Lavrov had announced May 7 in Moscow.
We will learn very quickly whether or not they and others are acting in good faith” to negotiate a settlement, Kerry said in remarks that also criticized Hezbollah and Iran for intervening directly on Assad’s behalf. “If they’re not, the world will know it.”
The prospects for a conference, intended to be held this month in Geneva, have appeared to wane as Assad’s government has grown more assertive and members of the Syrian opposition have balked.
Meanwhile, Syrian troops on Friday attacked a convoy trying to evacuate the wounded from a town near the border with Lebanon, killing at least seven people, as rebel reinforcements infiltrated the besieged area to fight government forces backed by Lebanese Hezbollah fighters, activists said.
The battle for Qusair has exposed the Shi’ite militant group’s growing role in the Syrian conflict, in which more than 70,000 people have been killed over the past two years.
Hezbollah initially tried to play down its involvement in Syria, but abandoned the attempt after dozens of its fighters were killed in the Qusair area and buried in large funerals in Lebanon.
Qusair-based activist Hadi Abdullah said he was with the convoy evacuating the wounded when troops started firing shells and machine guns. ‘‘Women and children jumped out of the cars and started running in fear,’’ he said.
About 800 wounded remained behind in the town’s rebel-held areas, said Abdullah, adding that the main makeshift hospital in Qusair and a home that had been turned into a clinic were hit.
Westerwelle also criticized Russia’s weapons delivery, saying Germany had raised the issue with the government of President Vladimir Putin.
“I would like to make this absolutely clear. We tell our Russian colleagues, don’t endanger the conference in Geneva,” he said. “The delivery of weapons to the Assad regime is totally wrong.”
The Russians have stated that Western and Arab military aid to the insurgency has endangered any hope of a diplomatic settlement. The European Union has just relaxed its arms embargo, and Britain has signaled that it is prepared to supply weapons to the rebels.
Russia’s support for the Assad government has long been a concern for the United States. In a statement Thursday, Caitlin Hayden, a National Security Council spokeswoman, also expressed concerns about the Syrian government’s “access to Russian banks.”
At the United Nations, Russia has opposed Jordan’s proposal that the Security Council undertake a fact-finding trip to Jordan, Turkey, and Lebanon to investigate the flow of refugees. Jordan had proposed the trip to draw attention to the refugee situation.
Lavrov has also backed the Syrian government’s opposition to proposed wide-ranging inspections to investigate whether it has used chemical weapons, calling it an effort by foes of the Assad regime to “politicize” the issue.
Russia has also delivered Yakhont antiship cruise missiles and SA-17 surface-to-air missiles to Syria. Israel attacked trucks carrying SA-17 missiles near Damascus in January, concerned they were intended for Hezbollah.
In another development with implications for Syria, the State Department on Thursday issued an annual report on terrorism that asserted the roles of Iran and Hezbollah, Assad’s regional allies in the conflict, had expanded.
Hezbollah, regarded by both the United States and Israel as a terrorist group, has sent hundreds of fighters into Syria to assist Assad’s forces as they battle an insurgency drawn largely from the country’s Sunni majority.
The fight has become increasingly sectarian, spilling into Lebanon, and in recent weeks has centered on Qusair, a strategically important town that has been under intensifying assault by Assad forces and their Hezbollah allies.
On Friday, the interim leader of the Syrian Coalition, the main umbrella opposition group, said about 1,000 insurgent reinforcements had broken through and joined their colleagues in Qusair.
The interim leader, George Sabra, also announced at a meeting in Istanbul that the Syrian Coalition had agreed to expand by adding 43 members of the Free Syrian Army, the principal insurgent force, which had been pushing for a greater role.