Syrian rebels guarantee safety of UN inspectors

Saleh said it is "critical" the U.N. inspection team reach the alleged attack site outside Damascus within 48 hours to gather as much evidence as possible on the attack. 

More than 1,000 Syrian civilians were reportedly massacred outside the capitol when Assad's forces launched poison gas against several rebel positions around Damascus. 

Russia, an important Assad ally for the duration of the now three-year conflict, has accused the Syrian opposition of preventing U.N. inspection teams from entering the attack sites. 

"It is directly preventing an objective investigation into the possible use of chemical weapons in Syria," according to a statement from the Russian Foreign Ministry, Reuters reports. 

While the Assad regime has denied the attack, the Obama administration is reportedly now exploring military options to end the civil war in the country. 

Members of Obama's national security team, including top officials from the Pentagon, State Department and intelligence community huddled at the White House for more than three hours, discussing the administration's options in Syria, The New York Times reported on Friday. 

President Obama is under intense political pressure to respond after warning Assad a year ago that using chemical weapons would be a “red line” that would prompt a U.S. response. 

However, with the end of the Iraq war and the withdrawal of U.S. troops from Afghanistan within the next year, the Pentagon is expressing concern over entering into another conflict in the Mideast. 

Any U.S. military intervention in Syria "would not be militarily decisive" in ending the civil war, but only draw American forces deeper into a conflict that is increasingly leaving Washington with no good options, Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said Monday. 

Dempsey and Defense Secretary Chuck HagelCharles (Chuck) Timothy HagelShould Mike Pompeo be confirmed? Intel chief: Federal debt poses 'dire threat' to national security Hagel: Trump is 'an embarrassment' MORE have stated the Obama administration should be given the chance to exhaust all diplomatic options to end the Syrian civil war. 

Both U.S. military leaders have also repeatedly urged caution over calls for military intervention in Syria, noting the intensely complex and unpredictable situation in the country.