UNITED NATIONS (AP) — The U.N. envoy for South Sudan said Wednesday that the country’s new coalition government faces “a daunting array of challenges” that will test its unity after six years of civil war.

David Shearer told the U.N. Security Council the most immediate priority is for the former warring leaders and parties to form a transitional government so the country can start advancing toward peace.

Shearer’s video briefing from South Sudan’s capital of Juba followed the Feb. 22 formation of a coalition government led by President Salva Kiir with opposition leader Riek Machar as his deputy. The arrangement had twice collapsed in fighting during South Sudan’s the civil war, which killed nearly 400,000 people and displaced millions.

The U.N. envoy welcomed the unity government, saying that while courage is often talked about in war, “peace also requires courage.”

“The doubters are telling us we have been here before,” Shearer said. “But it’s also important to acknowledge these are changed circumstances.”

He said it’s “fair” that the international community likely leans on the side of caution, “wary of repeating past mistakes.” But he warned the world’s nations against totally stepping back and waiting to see what happens before making a commitment to the new government.

“Our actions can push South Sudan further toward sustainable peace,” Shearer said. “Our inaction can help condemn it to failure.”

There were high hopes that South Sudan would have peace and stability after gaining its independence from neighboring Sudan in 2011. But it plunged into ethnic violence in December 2013 when forces loyal to Kiir, a Dinka, started battling those loyal to Machar, his former vice president who belongs to the Nuer people.

Following last month's agreement on a unity government, Shearer said the most urgent challenge is to move on transitional security arrangements.

But he said the government must also end impunity and corruption, move toward self-reliance, and ensure that all South Sudanese are part of the democratic process.

Shearer said the new government also faces “a precarious humanitarian situation in many states,” noting that an anticipated improvement in the harvest a year ago was quashed by extensive flooding.

The floods not only destroyed crops and killed livestock but they contaminated water supplies, worsening health conditions particularly for children and contributing to communal violence between herders, Shearer said.

“It is no coincidence that the most severe food insecurity conditions but also the heaviest fighting are in Jonglei state where livestock losses have undermined these societies’ social fabric which is centered around cattle,” he said.

Nonetheless, Shearer stressed that the unity government signals a new phase, with the peace agreement serving as a road map for the next three years.

U.S. Mission senior adviser Michael Barkin said the Trump administration is hopeful “that the people of South Sudan can now see a glimmer of hope and progress.”

Barkin said this is “a particularly sensitive time for implementing security arrangements,” citing the close proximity of government and opposition forces during their cantonment and training which creates “a high risk of conflict.”

South Sudan’s U.N. Ambassador Akuei Bona Malwal appealed to the international community for support “in order for this peace agreement to hold in the long run.”

He said the coming government of national unity needs technical, material and specialized expertise “to establish livable cantonment sites” for security forces, and for the return of displaced people inside South Sudan and refugees who fled to neighboring countries.

He appealed for more international support “for the sake of lasting peace and unity in South Sudan.”