Dubai: US President Barack Obama seemed determined to get hard evidence of the use of chemical weapons in Syria before escalating US involvement in the conflict-torn country.

“Knowing that potentially chemical weapons have been used inside of Syria doesn’t tell us when they were used or how they were used,” Obama said in Washington.

“This is going to be a long-term proposition. This is not going to be something that is solved easily overnight,” he added.

In Lebanon, Russian Deputy Foreign Minister Mikhail Bogdanov said claims that chemical weapons have been used in Syria should not become a pretext for a foreign military intervention in the country. “If there is serious evidence of the use of chemical weapons in Syria, it should be presented immediately and not concealed,” said Bogdanov.

Meanwhile, United Nations investigators will examine soil samples collected by western intelligence agencies and enter Syrian refugee camps in an effort to assess claims, Jeffrey Feltman, UN  under-secretary for political affairs, said.  They will got to refugee camps and potentially taking hair and other biological samples from survivors of alleged chemical attacks, he added.

Syria’s information minister said the accusations that the regime may have used chemical weapons are a “barefaced lie.”

“First of all, I want to confirm that statements by the US Secretary of State and British government are inconsistent with reality and a barefaced lie,” Omran Al Zohbi said.