US Secretary of State Mike Pompeo has been accused of hypocrisy after personally blocking the inclusion of Saudi Arabia on a list of countries that recruit child soldiers.

The case puts a spotlight on Washington’s close relationship with the Gulf tyranny as a UN investigator said there was “credible evidence” that Crown Prince Mohammed bin Salman was behind the murder of journalist Jamal Khashoggi.

In doing so the former CIA director dismissed advice from his own department that said the Saudi-led coalition was using underage fighters during its devastating war on Yemen.

State Department experts recommended adding Saudi Arabia to the list based on evidence from human rights organisations and news reports which suggested child fighters had been recruited from Sudan.

The recommendation from the department’s human trafficking office faced resistance from some officials who said it was unclear whether the child fighters were under the control of Sudanese officers or directed by the Saudi-led coalition.

As many as 14,000 Sudanese fighters have been deployed to fight in Yemen by the Saudi-led coalition since the end of 2016, including children as young as 14. They are offered payment up to $10,000 each.

Sudan, which has been excluded from the list for the past three years, was included.

The State Department’s global Trafficking in Persons report is set to be released today. Those included on the list are not able to receive US aid, training and weapons unless the president issues full or partial waivers of those sanctions based on the “national interest.”

A State Department official said: “The United States condemns the unlawful recruitment and use of child soldiers.”

Critics have accused Mr Pompeo of covering for the Saudi regime once again, having come under fire over arms sales to Riyadh in wake of the Khasogghi scandal last year.

The Washington Post journalist was brutally murdered and hacked to pieces in the Saudi consulate in Istanbul.

An independent UN report into the killing released by Agnes Callamard said yesterday there was “credible evidence” to investigate the role of Mr bin Salman.

It added there was “no reason why sanctions should not be applied against the crown prince and his personal assets” ahead of investigations.

The US has been reluctant to impose sanctions on Saudi Arabia and despite calls to halt weapons sales, Mr Trump has insisted US jobs rely on the deadly trade.

Earlier this month the Trump administration announced it would circumvent Congress and sell $8bn in new weapons to Saudi Arabia and the United Arab Emirates 

However a cross-party group of senators vowed to block the arms sales through the introduction of 22 “resolutions of disapproval,” one for each deal signed off by Mr Pompeo.