The U.S. State Department accused Russia of obstructing the UN Security Council from investigating all allegations of the use of chemical weapons in Syria.
State Department spokeswoman Jennifer Psaki said that the United States received conclusions from Russian experts saying that chemical weapons were used by Syrian opposition fighters. The United States insists that it was Bashar Assad's troops that used chemical weapons.
Russia had previously handed over the samples taken at the site of a possible chemical attack to UN experts. The attack took place in the suburbs of Aleppo. The analysis showed the presence of poison gas sarin in the samples. The UN launched an investigation into the use of poisoned weapons in Syria.
"The United States continues to have no reliable corroborated reporting to indicate that the opposition in Syria has used chemical weapons," Psaki insisted.
She also accused Russia of "blocking an effort by the Security Council to allow UN access into Syria to investigate any and all credible allegations," The Associated Press reports.