JUBA, May 13 (Xinhua) -- There should be no further delay in forming a new unity government in South Sudan beyond the six-month extension period, the UN, African Union (AU) and east African bloc Intergovernmental Authority on Development (IGAD) have told parties to the fragile 2018 peace pact.

A joint UN-AU-IGAD delegation led by UN Under-Secretary-General for Peacekeeping Operations Jean-Pierre Lacroix concluded a two-day visit to the conflict-torn east African country on Saturday to push for the implementation of the September 2018 peace deal.

The team said while they remain supportive of the six-month extension, the rival groups in South Sudan should redouble efforts in implementing the pact and avoid further delays.

Lacroix urged the warring factions to use the six-month period to move the pact forward and end the crisis facing the world's youngest nation.

"Our purpose is to be supportive so that the next six-month after this extension of the pre-transitional period will be used to generate substantial advances in the implementation of the peace agreement, in the improvement of the lives of millions and millions of South Sudanese," Lacroix said.

"We wanted also to say quite clearly that this extension should be the last one. We are expecting the parties now to do every effort possible, every sacrifice, so that we have the transitional government in place next November," said Smail Chergui, AU Commissioner for Peace and Security.

Signatories to the 2018 peace agreement on May 3 agreed to extend formation of the transitional government by six months following delays in the implementation of the pact.

But South Sudan's President Salva Kiir last week called for one-year delay instead, arguing that the six months may not be enough to implement the outstanding issues such as security arrangements that continue to threaten the fragile peace deal.

South Sudan descended into civil war in late 2013 and the conflict has created one of the fastest growing refugee crises in the world.

The UN estimates that about 4 million South Sudanese have been displaced internally and externally.

A peace deal signed in August 2015 collapsed following renewed violence in the capital Juba in July 2016.

Under the 2018 peace deal, opposition leader Riek Machar will once again be reinstated as Kiir's deputy.

Ismail Wais, IGAD special envoy to South Sudan, said more challenges awaits the peace deal in the coming months, urging the signatories to join hands and bring lasting peace to South Sudan.

"We have a lot to do and a long way to go. We are not at the end of the process. In fact, we are starting with very challenging activities," Wais said.

"We still urge the political parties, the mechanisms, also to do the rest at their level best to implement this process so that at least the people of South Sudan deserve what they really earned and that is, at least, peace in this country," he added.