President Salva Kiir, center, attends a ceremony marking the 34th anniversary of the Sudan People's Liberation Army at military headquarters in Juba, South Sudan, on May 18. (Jok Solomun/Reuters)

The Trump administration is welcoming a pledge from South Sudanese President Salva Kiir to allow free passage for humanitarian agencies that have struggled to reach some of the war-ravaged country's neediest people.

Kiir's written order promising "free, unimpeded and unhindered movement" for aid convoys followed months of international demands and a blunt warning from U.S. Ambassador to the United Nations Nikki Haley.

Haley had told Kiir during a visit in late October that his U.S.-backed government is at risk of losing future U.S. diplomatic and financial support. The United States, U.N. monitors and others blame Kiir for sanctioning ethnic warfare and atrocities against civilians.

"This is a good sign, but we must see actions — more than words — from President Kiir," Haley said Tuesday, in a statement to The Washington Post.

"The true test will be whether humanitarian assistance is actually allowed to get to the South Sudanese people in a consistent way. We will be watching, and we will continue to encourage President Kiir to do the right thing."

Haley plans a speech on the South Sudanese conflict as part of a program Wednesday at the U.S. Holocaust Memorial Museum. The focus on a conflict that some activists call genocide will include huge pictures documenting the largest humanitarian crisis in Africa projected on the museum's exterior walls.

Kiir's Nov. 9 decree directs that physical roadblocks be dismantled so that convoys can pass, and instructs "all levels of the Government" to help aid groups in their work. In the past, Kiir's central government in the capital, Juba, has sometimes pleaded ignorance of alleged obstruction or crimes by far-flung military or police agents.

"Anybody who intentionally obstructs the delivery of Humanitarian Aid and services or imposes taxes on Humanitarian Convoys shall be held accountable," the order said.

The order does not spell out what that means, but Kiir would have the power to fire or prosecute some wrongdoers.

Haley told reporters traveling with her to Juba that Kiir had seemed to understand that he has run out of excuses and that Washington had run out of patience with a leader it helped to install.

Access for humanitarian agencies was among the specific demands she made, along with an end to violence.

A U.N. report last month said Kiir's government bears "primary responsibility" for violence that has driven millions from their homes.

A confidential report to the U.N. Security Council also blamed Kiir's government of using food as a weapon of war, Reuters reported Friday.

A U.S. official confirmed the report, which spans activity in 2016 and 2017.

"Kiir's government has a terrible history of using food as a weapon. That must end," said the official, who requested anonymity because the report has not been publicly released.

Haley visited destitute South Sudanese refugees who had fled across the border to an overflowing camp in Ethi­o­pia and others who had sought refuge in a U.N.-assisted camp on the outskirts of Juba. Residents of both camps blamed Kiir's soldiers for atrocities.

U.N. Humanitarian Coordinator for South Sudan Alain Noudéhou also welcomed Kiir's order, "at a time when food insecurity continues to deteriorate and humanitarian organizations face pressure to expand their response."