Former President Jimmy Carter offered a damning indictment of United States (US) foreign policy and domestic affairs on Tuesday, saying money in politics makes the nation more like an “oligarchy than a democracy” and casting President Donald Trump as a disappointment on the world stage.

Carter's criticisms, offered at his annual presentation to backers of his post-presidency Carter Center in Atlanta, went beyond Trump, but he was particularly critical of the nation's direction under the Republican president's leadership.

The 39th president, a Democrat, offered this advice to the 45th: “Keep the peace, promote human rights and tell the truth.”

Though Carter, 92, did not explicitly mention Trump's threatening exchanges this summer with the North Korean dictator Kim Jong-Un, but said the US should engage directly with the insular leader and discuss a peace treaty to replace the cease fire that ended the Korean War in 1953.

“I would send my top person to Pyongyang immediately, if I didn't go myself,” Carter said, noting that he's been to the country three times, even as successive US administrations have refused to deal with the regime.

The North Koreans, Carter said, want a treaty that guarantees the US will not attack unless North Korea attacks the US or an ally, particularly South Korea.

“Until we talk to them and treat them with respect as human beings, which they are, I don't think we're going to make any progress,” Carter said.

He also dismissed Trump's optimism that he can engineer Middle East peace. Trump has tasked his son-in-law Jared Kushner with handling the issue that has vexed US administrations for generations, and has notably backed off the long-held US position calling for a two-state solution between Israel and the Palestinians.

Carter said he is “practically hopeless” that anything Trump comes up with would give “justice to the Palestinians.”

“I don't think Trump or his family members are making any process in that respect,” he said.

Carter also criticised both Israeli and Palestinian leaders for a lack of flexibility, but he singled out Israeli Prime Minister Benjamin Netenyahu, a Trump ally, for having “no intention at all of having a two-state solution.”

While the former president and his wife Rosalynn largely steer clear of partisan politics, long having yielded any active role in the Democratic Party, they maintain their high-profile advocacy through the Carter Center which focuses on human rights, public health and democratic elections.

On Tuesday, Carter defended the centre's role in monitoring the August presidential elections in Kenya that the country's Supreme Court later discarded. The court has ordered a new election.

The Carter Center's monitoring team, led by former Secretary of State John Kerry, said days after the vote that the process of casting paper ballots was fair, but that the electronic tabulations were “unreliable.”

Carter said on Tuesday that international monitors were not allowed to observe the counting process.

The centre also remains engaged in trying to end the Syrian civil war, Carter said. He noted that he and others from the centre have engaged Russian President Vladimir Putin and others trying to broker peace.

Carter touted a programme at his centre that tracks social media usage in the war-torn nation. By identifying the locations of individual posters with known political and military affiliations, Carter said, analysts can discern which factions control various cities and provinces. Carter said the centre shares that intelligence with the Pentagon, the State Department, various media outlets and foreign allies of the US.

Carter made no mention of ongoing inquiries into Russian interference in the 2016 US presidential campaign or potential ties between Russia and the Trump campaign.