But State Department spokesman Mark Toner on Tuesday only stressed the need to "see some progress on a cessation of hostilities in the coming days." He said he couldn't "say categorically that ... there must be a cessation of hostilities" by Friday.
Toner blamed Russia for the impasse, condemning it for "unacceptable" attacks on hospitals and civilians. Russia must exert influence with Syrian President Bashar Assad's government to halt its ground offensives, Toner said. Russia says it is targeting terrorists, not civilians.
Speaking after a U.S.-Asian summit in California, President Barack Obama echoed the criticism.
"Russia has been propping up Assad this entire time," Obama said. He described Russian President Vladimir Putin's decision to send troops and aircraft to Syria as "a testament to the weakness of Assad's position."
"A country has been shattered because Assad was willing to shatter it," Obama added. Russia, he said, "has been party to that entire process."
Despite all the recent talk of ceasefire, the conflict is threatening to escalate. Turkey said Tuesday it is pressing for ground operations in Syria amid fears that U.S.-backed Kurdish militants are making gains at the opposition's expense. Washington sees the Kurds as an effective fighting force against the Islamic State.
Little headway appears to have been made on securing humanitarian access to besieged areas throughout the country.
Last week's Munich agreement demanded that access be provided immediately amid Western charges that Assad is starving his opponents and civilians into submission. Toner said some aid has reached certain areas, despite no United Nations confirmation of successful deliveries. In Syria, U.N. peace envoy Staffan de Mistura said he hoped food and other supplies would make it through Wednesday.
The ceasefire announced by Secretary of State John Kerry and his Russian counterpart last week appears most unlikely at this point. Toner said a U.S.-Russian-led task force that is supposed to map out the details of the truce still hasn't even met. He expressed hope of an initial gathering Wednesday.
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