A senior Syrian official dismissed Israeli and US reports that President Bashar Assad’s regime had used chemical weapons, saying it was a “big lie” that Syria was blocking a UN investigation into the claims.

Deputy Foreign Minister Faisal Mekdad told Reuters that his government had an agreement with the UN, allowing the international body to examine allegations of chemical weapons use near Aleppo. However, according to Mekdad, matters were complicated when the UN wanted to expand its probe to include other allegations.

“We are ready to receive immediately the team to investigate the case of Aleppo,” Mekdad said, “to provide all the logistics, help and support and protection and it is the responsibility of the UN secretariat if this delegation doesn’t arrive in Syria.”

The UN would like its inspectors to additionally investigate claims of chemical weapons use in Homs last December. Officials in France and the UK have urged the UN to look into a third claim in Damascus.

Mekdad, a former Syrian ambassador to the UN, accused France and the UK of trying to complicate the UN mission, and said the two countries were preventing the emergence of evidence regarding rebel use of chemical shells. He provided no evidence for his assertions, according to Reuters.

In Damascus, a government official said Assad’s military “did not and will not use chemical weapons even if it had them.” Instead, he accused opposition forces of using them in a March attack on the village of Khan al-Assal outside of the northern city of Aleppo, the largest in Syria. The official said the Syrian army had no need to use chemical weapons because it can reach any area in Syria it wants without them.

He spoke to The Associated Press on condition of anonymity because he was not authorized to give official statements.

His comments were echoed by Sharif Shehadeh, a Syrian lawmaker, who said the Syrian army “can win the war with traditional weapons” and has no need for chemical weapons.

Syria’s official policy is not to confirm nor deny it has chemical weapons.

Shehadeh called the US claims “lies” and likened them to false accusations that Iraq possessed weapons of mass destruction — a claim US policymakers had used to justify the invasion of that country in 2003.

“What is being designed for Syria now is similar to what happened in Iraq when Colin Powell lied in the Security Council and said Iraq possesses weapons of mass destruction prior to the US invasion and occupation of that country,” he said.

On Thursday, US Defense Secretary Chuck Hagel said that the US intelligence community now believes Syria has likely used chemical weapons on a “small scale” against its civilians.

Hagel added that the use of chemical weapons “violates every convention of warfare.”

The statement came on the heels of a public declaration Tuesday by the Israeli army’s top intelligence analyst, that forces loyal to President Bashar Assad had used sarin gas against rebel forces and civilians, and may push the US closer to intervening in the two-year-old conflict.

The White House, however, said the news would not necessarily trigger a response.

US Secretary of State John Kerry said the Syrian regime had launched two chemical attacks.

Hagel, speaking to reporters in Abu Dhabi, said the White House had informed two senators by letter that, within the past day, “our intelligence community does assess, with varying degrees of confidence, that the Syrian regime has used chemical weapons on a small scale in Syria, specifically, the chemical agent sarin.”

Britain followed the statement by saying London also believed there had been chemical attacks.

“We have limited but persuasive information from various sources showing chemical weapon use in Syria, including sarin,” a statement by the Foreign Office said. “This is extremely concerning. Use of chemical weapons is a war crime.”

Sarin, used by Saddam Hussein in aerial strikes against Iraqi Kurds in 1988 and in a Japan terror attack in 1995, is a nerve agent that cripples the respiratory system. It is hundreds of times more toxic than cyanide and is considered a weapon of mass destruction.

No information was made public on what quantity of chemical weapons might have been used in Syria, or when this took place, or what casualties might have resulted.

Hagel and President Barack Obama have said in the past the use of chemical weapons would be a “game-changer” in the US position on intervening in the Syrian civil war.

However, the White House said Thursday the intelligence fell short of what was needed to cross Obama’s “red line” on Syrian chemical weapons.

“We are continuing to do further work to establish a definitive judgment as to whether or not the red line has been crossed and to inform our decision-making about what to do next,” a senior administration official told reporters, according to a report in Foreign Policy. “If we reach a definitive determination that this red line has been crossed, based on credible, corroborated information, what we will be doing is consulting closely with our friends and allies and the international community more broadly, as well as the Syrian opposition, to determine what the best course of action is.”

The Associated Press contributed to this report