The US government has said a major aid package to the Philippines worth hundreds of millions of dollars may not be renewed, due to concerns over the leadership of President Rodrigo Duterte.

The US embassy to the Philippines said there were “significant concerns” about civil liberties infringements in the country and confirmed a board of experts had deferred its renewal of the Millennium Challenge Grant for a further five years.

The grant, said to be worth over $430 million, is open to nations that "demonstrate a commitment to just and democratic governance, investments in its people, and economic freedom”. It is aimed at reducing poverty in deprived areas.

Rodrigo Duterte says he 'doesn't give a s*** about human rights' as 3,500 killed in war on drugs

"This decision reflects the board's significant concerns around rule of law and civil liberties in the Philippines," the embassy said in a statement.

"We will continue to monitor unfolding events in the Philippines, and [this] underscores that all country partners are expected to maintain eligibility, which includes not just a passing scorecard but also a demonstrated commitment to the rule of law, due process and respect for human rights.

"The Board’s deferral of a vote on the Philippines re-selection is not a suspension or termination of the Philippines’ MCC compact eligibility."

The US has been openly critical of Mr Duterte's violent "war on drugs", during which an estimated 5,900 people have been killed without trial in the space of five months.

The homes of more than 1.6 million drug suspects have been visited by police to invite them to surrender and stop using drugs, or disengage from the drug trade.

Mr Duterte responded by declaring the Philippines was to "separate" from the US in a diplomatic sense, after decades of close ties between the two countries.

The Millenium Challenge Corporation (MCC) meanwhile announced new grants had been given to Burkina Faso, Sri Lanka and Tunisia, with the Philippines still eligible for consideration in the future.

“By partnering with developing countries that meet rigorous standards for good governance, from fighting corruption to respecting the rights of women and the rule of law, we are maximising our ability to fight poverty and transform people’s lives,” MCC chief executive Dana Hyde added.

In October, Mr Duterte called US President Barack Obama "a son of a whore" and told him to "go to hell" following criticism of his policies.

The most controversial quotes from Rodrigo Duterte Show all 9 1 /9 The most controversial quotes from Rodrigo Duterte The most controversial quotes from Rodrigo Duterte On killing drug addicts “These sons of whores are destroying our children. I warn you, don’t go into that, even if you’re a policeman, because I will really kill you. If you know of any addicts, go ahead and kill them yourself as getting their parents to do it would be too painful” The most controversial quotes from Rodrigo Duterte Message to China “I will go there on my own with a Jet Ski, bringing along with me a [Phillipino] flag and a pole, and once I disembark, I will plant the flag on the runway and tell the Chinese authorities, ‘Kill me’ ” AP The most controversial quotes from Rodrigo Duterte Christmas message to law-breakers “If you do not want to stop, and just continue committing crimes, then this would be your last Merry Christmas” AP The most controversial quotes from Rodrigo Duterte On sex life “I was separated from my wife. I’m not impotent. What am I supposed to do? Let this hang forever? When I take Viagra, it stands up” AFP/Getty Images The most controversial quotes from Rodrigo Duterte On the drugs trade “None of my children are into illegal drugs. But my order is, even if it is a member of my family, ‘kill him'" AP The most controversial quotes from Rodrigo Duterte Insulting the Pope “We were affected by the traffic. It took us five hours. I asked why, they said it was closed. I asked who is coming. They answered, the pope. I wanted to call him: ‘Pope, son of a wh**e, go home. Do not visit us again’” AFP/Getty Images The most controversial quotes from Rodrigo Duterte Joke about rape “I saw her face and I thought, 'What a pity... they raped her, they all lined up. I was mad she was raped but she was so beautiful. I thought, the mayor should have been first” AFP/Getty The most controversial quotes from Rodrigo Duterte Insulting Barack Obama "Mr Obama should be respectful and refrain from throwing questions at me about the killings, or son of a bitch, I will swear at you in that forum" REUTERS The most controversial quotes from Rodrigo Duterte On Abu Sayyaf Islamic militants "If I have to face them, you know I can eat humans. I will really open up your body. Just give me vinegar and salt, and I will eat you. If you annoy me to the fullest... I will eat you alive. Raw" EPA

The president has since courted favour from the governments of Russia and China, which have suggested they are willing to cooperate with Mr Duterte and provide aid.

Following the election of Donald Trump, Mr Duterte congratulated the President-elect on his success and hinted at a possible close partnership between the two in the future.

In October, Amnesty International said Mr Duterte’s “first 100 days as President had been marked by state-sanctioned violence on a truly shocking scale”.