Arab countries engaged in a rapprochement with President Bashar Al Assad should “get something” in return, a senior US official said on Thursday, accusing his Syrian regime of being behind an illegal drug trade devastating the region.

Barbara Leaf, Assistant Secretary of State, said the US had sent a message that it would not follow suit by its recent imposition of sanctions on two Assad family members for their suspected role the smuggling of the amphetamine known as Captagon.

Ms Leaf, who has visited in Jordan, Egypt, Libya, Lebanon, and Tunisia in the past two weeks, said the drug was “a new, terrible scourge across the region” and blamed much of its trade on the Assad government.

“The profiting from the Captagon trade is just another terrible example of why this [Syrian] regime deserves to be treated as the rogue it is,” said Ms Leaf, whose portfolio is the Near East region.

“We don’t intend to normalise,” she said from London. “This regime is such a disaster for its people but also for its neighbourhood.”

A drive for region-wide normalisation with Damascus has accelerated in the past two months after the earthquake last month affected parts of Syria and made it easier to deal more directly with the Syrian government.

This month, Saudi Foreign Minister Prince Faisal bin Farhan said consensus was building in the Arab world that talks with Damascus were needed, particularly on the humanitarian situation in Syria.

But Prince Faisal said it was “too early to discuss” the return of Syria to the Arab League.

Saudi Arabia is the main market for Captagon manufactured in Lebanon and Syria. Arab officials say areas in and around Damascus have become the manufacturing centre for the narcotic, with billions of dollars’ worth flowing through Jordan and on to Saudi Arabia, as well as by sea.

Many Arab countries downgraded ties with the regime in Damascus for its violent suppression of the 2011 revolt against five decades of Assad family rule.

Ms Leaf said Washington has had discussions with its Middle East allies about “their shift in policy”.

“They want to try engagement,” she said. “Our approach on that score is that make sure to get something for that engagement.

“I would put ending the Captagon trade right at the top, alongside the other issues … that go to providing relief to the Syrian people from the terrible decade of oppression that they suffered.”

She cited the regime’s failure to adhere to UN Security Council Resolution 2254, which calls for an unidentified political transition in the country as well as the release of prisoners, which human rights groups say number in the thousands.