The White House said on Friday it was working with partners to ratchet up pressure on Syria to accelerate removal of its chemical weapons after the United States accused it of deliberately stalling an international disarmament deal.
The Obama administration stepped up criticism of President Bashar al-Assad's government as Secretary of State John Kerry was due to meet Russian Foreign Minister Sergei Lavrov in Munich on Friday amid a U.S. push for Moscow to do more to win cooperation from its ally Damascus.
Russia earlier rejected U.S. charges that Syria is dragging its feet on giving up chemical weapons, saying that a June 30 deadline to destroy Assad's arsenal of toxic agents remains viable despite delays.
"Syria must immediately take the necessary actions to comply with its obligations," White House spokesman Jay Carney said at a briefing in Washington.
"We all know that the Syrian regime has the capability to move these weapons," Carney said. "We're going to continue to work with our partners on this to keep up the pressure on the Assad regime."
But Carney stopped short of threatening any specific action if Syria did not get chemical weapons deliveries on track.
Asked what the consequences would be if Syria did not take action, he said: "The United States and our partners in this effort will insist that Syria meet its commitments."
Assad's decision in September to give up chemical arms helped him avoid threatened U.S. air strikes in retaliation for a poison gas attack near Damascus in August that killed hundreds of people, many of them women and children.
President Barack Obama this week touted the chemical weapons agreement as one of the few U.S. diplomatic achievements on Syria, but the State Department said on Thursday just 4 percent of Syria's deadliest chemical agents has been shipped out of the country for destruction at sea.
The United States has few good choices to force Assad to comply. Americans are weary of war and Congress is unlikely to go along with any new military engagement in the Middle East.
Russia has been Assad's most powerful diplomatic backer during the nearly three-year-old conflict in Syria that has killed 130,000, using its veto power in the U.N. Security Council to block Western-backed efforts to push him from power or impose sanctions.
But even as Moscow defended Syria over the chemical weapons program, it runs the risk of diplomatic embarrassment if the international community broadly deems Assad to be in violation of a deal Russia brokered in the first place.