The government of South Sudan has urged the United States to be patient as its leaders work to achieve peace.
The US, a key supporter of South Sudan, Monday recalled Ambassador Thomas Hushek for consultations as it communicated its frustration over South Sudan leaders' failure to form a government.
US Secretary of State Mike Pompeo wrote on Twitter that he recalled the ambassador "as we re-evaluate our relationship with the government of South Sudan."
In an interview with the East African on Tuesday, Ministry of Foreign Affairs and International Cooperation spokesperson Mawien Makol described the withdrawal as a diplomatic concern to the government of South Sudan.
"We are urging the United States to reconsider the withdrawal, we are appealing to them to support the peace process... The country still needs their support because we are here to implement in 100 days and we are hopeful that these 100 days will be final and we will be able to established the R-TGoNU timely," he said.
Mr Mawien said the government accepted the 100-day extension because it was a collective need by some parties to the peace deal, and it would help the country achieve durable peace.
The United States, which contributes about $1 billion a year in mostly humanitarian aid for the young country, has been especially vocal in its exasperation over the lack of progress in South Sudan.
South Sudan President Salva Kiir and opposition leader Riek Machar fell out in 2013 - two years after the largely Christian nation won independence from Sudan with strong US support - sparking a conflict that has left hundreds of thousands dead.
The two leaders missed a November 12 deadline to form a unity government. African mediators gave them another 100 days, the second extension.
While in Washington, Ambassador Hushek will meet senior US government officials as part of the re-evaluation of the US relationship with South Sudan, read a statement issued by the Department of State on Monday.
Last month, the US Senate introduced a bipartisan resolution in support of the peace process in South Sudan.
South Sudanese political analyst James Okuk said the recent statement by the US government is an indication that the Trump administration has lost trust in the ability of President Kiir and Mr Machar to work together.
Dr Okuk warned that if the two leaders do not form a unity government at the lapse of the 100-day extension, they may face sanctions.
In August this year, the United States threatened to impose fresh sanctions against South Sudan leaders if they fail to form a coalition government as scheduled.
The five-year civil war, which was triggered by power wrangles between Mr Kiir and Mr Machar has reportedly caused nearly 400,000 deaths.
The coalition government to be formed on February 22 next year is expected help stabilise the country and bring to an end the suffering of the people.