RNA - The decision, which came after a fierce internal debate, could prompt new accusations by human rights advocates and some politicians that US President Donald Trump's administration is prioritising security and economic interests in relations with oil-rich Saudi Arabia, a major Washington ally and arms customer.
Pompeo's move comes amid heightened tensions between the United States and Iran, Saudi Arabia's bitter regional rival.
US State Department experts recommended adding Saudi Arabia to the soon-to-be-released list based in part on news reports and human rights groups' assessments that the kingdom has hired child fighters from Sudan to fight for the US-backed coalition in Yemen, the four sources stated.
The experts' recommendation faced resistance from some other State Department officials who, according to three of the sources, argued that it was not clear whether the Sudanese forces were under the control of Sudanese officers or directed by the Saudi-UAE coalition.
A New York Times report in December cited Sudanese fighters saying their Saudi and United Arab Emirates commanders directed them at a safe distance from the fighting against the coalition's foes.
"The allegations of recruiting child soldiers are completely incorrect and are not based on any evidence or factual findings," Colonel Turki al-Malki, a spokesman for the Saudi-led coalition noted, instead accused the Saudis' foes of using child fighters in Yemen.
Pompeo rejected the recommendation from the experts, who are from the State Department's anti-human trafficking office, said the four sources who spoke on condition of anonymity.
The office has a key role in investigating the use of child soldiers worldwide.
"The United States condemns the unlawful recruitment and use of child soldiers. We place great importance on ending the practice wherever it occurs," a State Department official stated in response to Reuters' questions.
The official, however, did not specifically address the Saudi decision or whether any consideration was given to Riyadh's security ties to Washington.
Instead of adding Saudi Arabia to the list, Sudan will be reinstated after being removed last year, three of the sources added.
A spokesman for Sudan's paramilitary Rapid Support Forces, which has contributed fighters to the Yemen war, said the force is affiliated with Sudan's military.
"Based on Sudanese laws, it does not recruit minors," he stated, but did not directly respond to a question on who controlled Sudanese forces in Yemen.
The UAE government did not respond to a request for comment.
The child soldiers list will be part of the State Department's annual global Trafficking in Persons report, which the sources said is expected to be released as early as Thursday.
The Child Soldiers Prevention Act of 2008 requires the State Department to report annually on countries using child fighters, defined as "any person under 18 years of age who takes a direct part in hostilities as a member of governmental armed forces".
Foreign militaries on the list cannot receive US aid, training and weapons unless the president issues full or partial waivers of those sanctions based on "national interest".
Trump and his predecessors have done this in the past for countries with close security ties to the US.
"This decision shows clearly that the Trump administration is using political manipulation and dismissing evidence - at the expense of kids - in order to protect Saudi Arabia," noted Sarah Margon, director of Human Right Watch's Washington office.
While internal debates over issues like child soldier violations often take place before the release of the annual State Department list, this one was especially heated, several of the sources stated.
Since the end of 2016, the Saudi-led coalition has deployed as many as 14,000 Sudanese troops at any given time, including children as young as 14, to fight in Yemen, offering payments of up to $10,000 per recruit, according to the New York Times.
The article cited Sudanese fighters who had returned home and Sudanese politicians.
In Washington, DC, the Yemen conflict is a contentious issue well beyond the State Department.
Republican and Democratic politicians, citing US intelligence agency evidence of Saudi Crown Prince Mohammad bin Salman's role in the 2018 killing of Saudi journalist Jamal Khashoggi and angered by the civilian toll from the Saudi-UAE air campaign in Yemen, have ramped up efforts to block Trump's multibillion-dollar arms sales to Saudi Arabia.
Congressmen Tom Malinowski and Ted Lieu organised a letter to Pompeo from more than a dozen politicians in March that said they were "gravely concerned by credible reports" of the Saudi-UAE coalition deploying Sudanese child fighters in Yemen.
They called for a US investigation, including into whether they had been armed with US-made weapons, and also asked for an inquiry into "credible evidence of Houthi forces forcibly conscripting minors into combat".
Sudan sent thousands of troops to Yemen with the Saudi-UAE coalition that intervened in the war in 2015 against the Houthis.
The Trump administration has faced controversy in the past over its handling of the child soldier issue.
Reuters reported in 2017 that then-Secretary of State Rex Tillerson opted to remove Iraq and Myanmar from the child soldiers list and rejected a recommendation to add Afghanistan to it, despite the department publicly acknowledging that children were still being conscripted in those countries.
The State Department announced at the time that while the use of child soldiers was "abhorrent", it was still in "technical compliance with the law".
Pompeo, who succeeded Tillerson, reinstated Iraq and Myanmar on the list last year.