Seeking to mollify international officials impatient with Syria for missing deadlines to destroy its chemical weapons, Russia said Tuesday that the Syrian government plans to send a shipment out of the country this month and export its entire stockpile by March 1.

Russia's deputy foreign minister, Gennady Gatilov, who conveyed the new pledges, also defended the Syrian government's explanations for the missed deadlines, arguing that security dangers posed by the Syrian civil war had created enormous problems in transporting the chemicals to the port of Latakia, where an international flotilla awaits them.

"There really are difficulties linked to the need to provide security for this operation," Gatilov said.

Gatilov's remarks appeared to be in response to the exasperation expressed last week by the United States over Syria's slow pace in exporting about 1,200 tons of chemical material, half of it considered especially dangerous.

U.S. officials had asked Russia to use its influence with President Bashar Assad of Syria to compel him to fulfill his pledges.

Assad said in September, when Syria agreed to join the global treaty that bans the production and use of chemical weapons, that his government would destroy the munitions.

Despite a negotiated timetable, Syria missed a Dec. 31 deadline to export the most dangerous chemicals and will miss a second deadline Wednesday to export all the chemicals. Diplomats say that only two small shipments, 4 percent of the total, have been removed from the country so far.

The Organization for the Prohibition of Chemical Weapons, a group based in The Hague, Netherlands, that is working with the United Nations to oversee the destruction of the Syrian stockpile, added its voice to the criticism Friday, when Ahmet Üzümcü, its director general, said, "The need for the process to pick up pace is obvious."

The group cautiously welcomed Gatilov's assertions. It "looks forward to receiving such a plan from the Syrian authorities," said Michael Luhan, a spokesman.

After decades of denying that it even possessed chemical weapons, the Syrian government reversed itself after a chemical attack Aug. 21 that created a global uproar. The government and the opposition seeking to topple it blamed each other for the attack.

Under a Russian-American agreement that averted a U.S. military strike on Syria, Assad promised to destroy the entire arsenal by June 30.

Russia has been a major participant in the effort to export the chemicals, providing armored vehicles for the overland transport convoys and naval escorts to vessels carrying the chemicals from Syria.