The president of South Sudan and his former vice president signed a peace deal on Wednesday in a bid to end their country’s protracted civil war.

The rivals — President Salva Kiir and former Vice President Riek Machar, who leads the largest rebel group fighting the government — met for the first time in two years last week. The civil war has lasted for more than four years and has plunged South Sudan, the world’s youngest country, into a humanitarian crisis.

Despite the agreement, signed in neighboring Sudan, many worry that a lasting resolution to the conflict is still a long way off. Peace deals signed by both leaders have fallen apart in the past, and the war now involves numerous smaller parties. Just two years ago, the pair struck a similar agreement that soon unraveled.

Jacob Bul, co-founder of a South Sudanese artists’ collective called Ana Taban, or I’m Tired, said the country needed a peace deal that represented the interests of all people in South Sudan, rather than the interests of a few.