“Any money going to Assad and his allies shows that the UN is not impartial but is in fact helping the largest player in the conflict,” said Kathleen Fallon, a spokeswoman for The Syria Campaign, an independent advocacy group. “The regime has been responsible for the majority of the deaths, and they are being rewarded. It sends the wrong message.’’

UN officials point to the difficulty of operating outside the auspices of governments in countries such as Syria, and the premium placed on protecting its staff. In 2003, when the US invasion of Iraq had begun evolving into a civil war with parallels to the Syrian conflict, UN envoy Sergio Vieira de Mello and several members of his staff were killed by a car-bomb attack on the Baghdad hotel they were using as a base.

“We source locally and there are many places where the local economy is either state-owned or we have very limited options,’’ said Stephane Dujarric, the UN’s chief spokesman. Of UN spending at the Four Seasons, co-owned by the tourism ministry and Saudi billionaire Prince Alwaleed bin Talal, he said: “that’s one place in Damascus that has been cleared for security.’’

The UN spent US$140 million on goods and services in Syria last year, according to the report.

Syriatel, which belongs to Makhlouf, was paid US$164,300 by three different UN bodies including the refugee agency UNHCR and the children’s relief organization UNICEF. Another UN agency, the United Nations Relief and Works Agency for Palestine, paid US$105,043 to Qasioun, a security firm he owns.

Makhlouf, one of Syria’s richest businessmen, has been on the US Treasury’s blacklist since 2008. Qasioun was specifically listed by the Treasury’s Office of Foreign Assets Control in December.

He’s “known as Mr 10 per cent in Syria because he has an interest in so much of the economy,” said Joshua Landis, a Syria expert who heads the Center of Middle East Studies at Oklahoma University. “The key to getting anything done in Syria is to grease the palms of the powerful.’’

Muhammad Hamsho, another regime insider, was added to the US sanctions list in 2011. The EU followed suit in 2015, saying he “benefits from and provides support to the Syrian regime through his business interests.’’

Hamsho controls Jupiter Investment Co, according to the U.S. and EU. The company was awarded two contracts for office space and accommodations by the UN’s peacekeeping operation monitoring the Golan Heights region between Syria and Israel. The UN’s procurement report for 2016 said the company received contracts worth US$1.5 million. A UN spokesman said by email that the world body had options to extend the leases, which have a total value of US$7.7 million.

A US Treasury spokesman said that US sanctions on Syria “prohibit American persons from engaging in a wide range of transactions, and block the Syrian government from certain activities,” while declining to comment on specific companies.

Meanwhile, UN efforts to bring food and medical relief to Syria have been physically targeted by Assad’s government - and also criticised by his opponents.

Syrian and international non-governmental organisations have complained that aid has disproportionately gone to government-controlled areas. They received 88 per cent of food aid distributed from Damascus in April 2016, according to a World Food Program report. In September, 73 NGOs wrote to the UN condemning the manipulation of relief efforts.

One local group that handled aid deliveries is the Syria Trust for Development, a charity headed by Asma al-Assad, Bashar al-Assad’s wife. It was awarded US$751,129 last year by the UN Office for the Coordination of Humanitarian Affairs.

“The UN wants to be as close as possible to the regime to get things done,’’ said Reinoud Leenders, an associate professor at the Department of War Studies at King’s College in London. Still, he said, it’s “puzzling’’ that the UN is ignoring American blacklists. “Especially considering that the US. is its main funder.’’