JUBA, South Sudan — South Sudan on Wednesday rejected a US proposal for the UN Security Council to send 4,000 additional troops to the East African country to restore calm, saying it ‘‘seriously undermines’’ its sovereignty and threatens a return to colonialism.

Government spokesman Michael Makuei said the proposal gives the United Nations the ability to govern. The proposal also calls for a vote on an arms embargo on South Sudan if Secretary General Ban Ki-moon reports within a month that authorities have blocked the regional force.

The Security Council could vote Friday on the proposal, which comes after a former US special envoy suggested last month that the UN and African Union temporarily administer the country after fighting broke out once again.

South Sudan’s pushback comes as UN officials say the government has begun a crackdown that includes seizing dozens of passports of UN workers and imposing restrictions on travel and delivery of food aid.

Deadly fighting in the capital, Juba, last month raised fears of a renewed civil war after an August 2015 peace deal and worsened a humanitarian crisis.

Rebel leader and former first vice president Riek Machar fled during the fighting and says he will return only when regional peacekeepers secure the capital.

An East African political body, IGAD, last week said South Sudan had agreed to a regional force, but Makuei on Wednesday disagreed and said the government had not been consulted.

Under the US proposal, the regional force would report to the UN force that numbers more than 12,000 peacekeepers but has been criticized for not protecting civilians. The regional force would protect the airport and promote ‘‘safe and free movement’’ in and out of the capital.

Associated Press