Yemeni supporters of the Houthi movement take part in a rally to commemorate the fourth anniversary of the start of the uprising that forced out president Ali Abdullah Saleh in Sanaa on February 11, 2015.

The U.N. Security Council is due to adopt a resolution Sunday urging the Shiite militiamen behind a power grab in Yemen to step down, release government officials and negotiate, diplomats said.

Calling for the militia, known as Houthis, to act “immediately and unconditionally,” the council’s 15 member states will demand the group “withdraw their forces from government institutions… and relinquish government and security institutions,” according to a draft of the resolution.

Yemen has descended into chaos since the Houthis seized Sanaa in September, sweeping into the capital unopposed from their northern stronghold. Despite a U.N.-brokered deal, they have refused to withdraw their fighters from the city.

The crisis escalated after the militia last month took control of key government buildings, prompting Western-backed President Abedrabbo Mansour Hadi to tender his resignation.

The Houthis must “engage in good faith in the U.N.-brokered negotiations” being led by U.N. special envoy Jamal Benomar and “safely release President Hadi, Prime Minister (Khalid Mahfoudh) Bahah, members of the cabinet and all individuals under house arrest or arbitrarily detained.”

The member states also alluded to sanctions, expressing their “readiness to take further steps in case of non-implementation,” but made no explicit reference to Chapter Seven of the United Nations Charter, which allows for economic and military pressure to enforce council decisions.

Yemen’s neighbors Saturday, at a Riyadh meeting of the Gulf Cooperation Council, had urged the U.N. to evoke Chapter Seven.

According to Western diplomats, Russia, under U.S. and European sanctions over Crimea and eastern Ukraine, was reluctant to vote for sanctions.

The text marks the U.N. Security Council’s first resolution since the Houthis took control of the country, in a power grab that Washington and Gulf countries have described as a coup.

The council was due to adopt the text on Sunday in New York, according to diplomats.

U.N. Secretary General Ban Ki-moon has warned that Yemen is falling apart and said Thursday that Western-backed Hadi should be restored to power.

The Houthis, who have expanded their presence into central and western Yemen, resumed U.N.-brokered talks on Monday.

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