The massive aid operation for war-torn Yemen is under severe threat in the face of mounting obstruction from Huthi rebels, officials told AFP Tuesday ahead of a crunch meeting expected to be held in Brussels.

Humanitarian agencies describe a deteriorating situation in the Huthi-controlled north where aid workers face arrest and intimidation as they attempt to distribute food to millions in dire need after five years of conflict.

But the Yemen government sounded the alarm at reports the United States is considering suspending much of its humanitarian assistance by March 1 in response to the pressures that include a new two-percent rebel "tax" on assistance projects.

Abdul Raqib Fateh, a minister and the head of Yemen's relief committee, said although the government believes the militia misuses aid "as a cover to finance its war efforts", cutting off supplies would hurt the wrong people.

"Scaling back on aid in governorates under Huthi control will affect citizens, not the armed Huthi militias," he told AFP.

The Huthis hit out at the criticism, which includes allegations of systematic interference and layers of bureaucracy imposed by SCMCHA, the rebel's aid body that was created late last year.

"Some UN agencies play a political role and use aid as a card with which to threaten the Yemenis," said the head of SCMCHA, Abdul Mohsen al-Tawoos.

"This blackmail of reducing aid doesn't work on Yemenis, and if they continue with this threat, then things will turn against them," he said according to Huthi media.

- 'Violence and coercion' -

Allegations of aid being diverted and obstructed are not new in Yemen, which has been driven to the brink of famine during the long-running crisis which pits the Iran-backed Huthis against the government and a Saudi-led military coalition.

One battleground has been expired food, with the Huthis accusing the United Nations of distributing maggot-ridden rice and flour, and aid workers saying that supplies due for needy families had been held for months until they spoiled.

The UN World Food Programme, which feeds 12 million Yemenis a month, halted deliveries in Huthi-controlled areas for two months last year as it pushed for a biometric registration scheme to avoid the diversion of supplies meant for Yemeni civilians.

However, the New Humanitarian news agency last week cited a United Nations report that said threats to aid workers were increasing along with bureaucratic delays that bogged aid agencies down.

"The issue of the manipulation of beneficiary lists and/or pressure to share these lists is of particular concern, and cases involving the use of violence and coercion at aid distribution points have increased in 2019," it quoted the unreleased report as saying.

- Red lines -

The thorny topic of how to respond to the pressure, and the implications of suspending humanitarian aid in a country already on the brink, will be discussed at a meeting of aid agencies and donors in Brussels which opens on Thursday.

"Too many red lines have been crossed by the authorities," a Sanaa-based aid worker told AFP. "Our job is to get aid to people. What do we do when we're being blocked from doing that?"

Humanitarian officials say they are hoping there is still room for negotiation to avoid a suspension, but that the outlook will be clearer after the Brussels meeting.

"I think we're all hoping that it will not come to that," one aid official said. "We are trying to coordinate with all the donors including the US to come up with a more unified approach."

Lise Grande, the UN resident coordinator for Yemen, indicated that the agencies would be forced to act if they cannot uphold their principles in Yemen.

"If we reach a point where the operating environment doesn't allow us to do that, we do everything we can to change it," she told the BBC.

"We may have to go in a different direction for a little while until we can get those conditions back in place. That's our responsibility," she said. "We are committed to find ways to cooperate."