The United States said on Wednesday that South Sudan’s leaders should respect their commitment to establishment of a “hybrid court” to adjudicate charges of war crimes.

“We’re disappointed,” State Department deputy spokesman Mark Toner said in response to President Salva Kiir’s and Vice President Riek Machar’s joint rejection of the court in a commentary in the New York Times on June 7.

“We firmly support the African Union’s efforts to establish this hybrid court,” Mr Toner said. “And we expect the parties to fulfil their responsibilities.”

He noted that creation of the court is one of the elements in the August 2015 South Sudan peace agreement signed by President Kiir and Dr Machar.

The Obama administration’s defence of the proposed court may make it difficult for South Sudan’s factions to avoid accountability for atrocities that both sides are said to have committed.

President Kiir and Vice President Machar argued that the court, consisting of judges from South Sudan and other African countries, would impede reconciliation in the aftermath of a civil war that took tens of thousands of lives.

They instead called for creation of “a national truth and reconciliation commission modelled on those of South Africa and Northern Ireland.”

READ: South Sudan grapples with issue of perpetrators of crime

The State Department said in response that the US is not opposed to such a commission, which, it said, “could be an important part of this peace agreement.”

But the hybrid court and a truth-and-reconciliation body are “not mutually exclusive,” Mr Toner said. “There needs to be accountability.”

President Kiir and Dr Machar, bitter foes in a 30-month civil war, jointly called for cancellation of their prior commitment to accept a “hybrid court” with the power to try war crimes.

They instead urged creation of “a national truth and reconciliation commission.”

“Bringing South Sudan together can be truly guaranteed only through one route: an organised peace and reconciliation process with international backing,” they wrote on Tuesday.

Such a body would not impose punishments for atrocities committed during the conflict between government forces commanded by President Kiir and rebels loyal to Mr Machar.

Both sides carried out widespread killings of civilians and rapes, according to reports by the United Nations and monitoring groups. Estimates of the death toll in the conflict run to thousands.

Human Rights Watch has since blasted the Kiir-Machar proposal as “a self-serving attempt to evade justice at the expense of victims of atrocities, which can only be expected to fuel further abuses.”

Establishment of a hybrid court is one of the elements in the August 2015 peace agreement signed by Mr Kiir and Dr Machar.

That agreement “endows the African Union with the responsibility to set up an African-South Sudanese hybrid court to try perpetrators of the worst crimes,” said Elise Keppler, international justice associate director at Human Rights Watch.