The Syrian government has denied permission to a U.N. mission ready to investigate alleged chemical attacks that have occurred in recent months in the country. Both Syria’s government and opposition requested that the U.N. form a mission to investigate the use of chemical weapons after trading blame over a March attack in Khan al-Assal—a village outside Aleppo—which killed at least 31 people.

However, Syria is now denying the team entry into the country over concerns of the U.N. widening the investigation to include other alleged chemical attacks—such as an attack near Damascus on the same day as the Aleppo attack and another from Homs in December, over which the government and opposition have also traded blame—brought to U.N. attention by Syria’s opposition.

Both Britain and France wrote to U.N. Secretary General Ban Ki-moon after the Aleppo and Damascus attacks, urging the mission to include all three reported instances of chemical weapons use in the country. Britain, France, and the U.S. have also provided Ban with intelligence about the possible use of chemical weapons in Aleppo and Homs.

Western powers have been particularly concerned over any use of chemical or biological weapons in Syria, since the country is believed by Western intelligence agencies to possess one of the largest undeclared stockpiles of chemical and biological weapons in the world. U.S. President Barack Obama has also already stated that the confirmed use of chemical weapons in Syria would be a “game changer,” which some have interpreted to indicate U.S. military intervention in Syria’s civil war.

Syria is amongst eight countries that did not participate in the 1997 Chemical Weapons Convention, which bans the use of such weapons internationally and, as of February, has seen to the destruction of 78% of the world’s declared chemical weapons stockpiles.

‘Weapons of Mass Destruction’

Syria’s government, according to the Guardian, argues that the inclusion of the other attacks in the investigation “might allow the U.N. mission to spread all over the Syrian territories,” which it claims “contradicts the Syrian request from the U.N.” and “constitutes a violation of the Syrian sovereignty.” The Syrian government has hinted at a hidden Western agenda in the mission and likened the situation to the investigation for chemical and biological weapons in Iraq, particularly Ban’s submission to Western states “known for their support for the shedding of Syrian blood with the aim of diverting [the probe] from its true content.”

Russia—a steadfast ally of Damascus throughout Syria’s two-year civil war—has echoed this claim, suggesting that “Western countries are using the specter of weapons of mass destruction to justify intervention in Syria, as they did in Iraq,” according to Reuters.

Headed by Ake Sellstrom, a former U.N. weapons inspector in Iraq, the U.N. mission is comprised of 15 inspectors, chemists, and medical experts—none of whom are from permanent members on the U.N. Security Council. The Organization for the Prohibition of Chemical Weapons (OPCW)—which oversees the 1997 Chemical Weapons Convention—has prepared and sent the team to Cyprus, where it currently awaits a decision between Syria and the U.N.

Syria and the U.N., however, are at an impasse: Ban Ki-moon believes there is sufficient evidence to investigate at least the Aleppo and Homs attacks and has said that all implicated sites “should be examined without delay, without conditions and without exceptions.” Syria, however, will not allow the mission into the territory unless it can guarantee that the mandate only covers the Aleppo attack.

A decision needs to be made soon, regardless: Ralf Trapp, an expert on chemical and biological weapons and a former official of OPCW, predicted immediately after the Aleppo and Damascus attacks that the time frame of the U.N. mission, though critical, would likely take weeks. And the longer the investigation is halted also compounds the evidence lost and, therefore, the further testing needed to collect such data: “Each day lost will influence the speed with which the investigation can be concluded,” he said, according to NBC, “because as more time elapses before biological sampling occurs, more sophisticated DNA and other toxicological testing is required.”

The Syrian government is unlikely to budge, especially while being backed by Russia and given preliminary evidence that suggests the chemicals used in the Aleppo attack—but not necessarily those in Damascus or Homs—were rudimentary and likely the product of an Islamists. One would hope that Ban would take into account the fact that the team has unfettered access to at least one site for now, lest Syria deny the investigation altogether.

Leslie Garvey is a contributor to Foreign Policy in Focus and Focal Points.