Britain and other European governments should break from the US over the international embargo on Gaza, former US president Jimmy Carter told the Guardian yesterday. Carter, visiting the Welsh border town of Hay for the Guardian literary festival, described the EU's position on the Israeli-Palestinian dispute as "supine" and its failure to criticise the Israeli blockade of Gaza as "embarrassing".

Referring to the possibility of Europe breaking with the US in an interview with the Guardian, he said: "Why not? They're not our vassals. They occupy an equal position with the US."

The blockade on Hamas-ruled Gaza, imposed by the US, EU, UN and Russia - the so-called Quartet - after the organisation's election victory in 2006, was "one of the greatest human rights crimes on Earth," since it meant the "imprisonment of 1.6 million people, 1 million of whom are refugees". "Most families in Gaza are eating only one meal per day. To see Europeans going along with this is embarrassing," Carter said.

He called on the EU to reassess its stance if Hamas agreed to a ceasefire in Gaza. "Let the Europeans lift the embargo and say we will protect the rights of Palestinians in Gaza, and even send observers to Rafah gate [Gaza's crossing into Egypt] to ensure the Palestinians don't violate it."

Although it is 27 years since he left the White House, Carter recently met Hamas leaders in Damascus. He declared a breakthrough in persuading the organisation to offer a Gaza ceasefire and a halt to Palestinian rocket attacks on Israel if Israel stopped its air and ground strikes on the territory.

Carter described western governments' self-imposed ban on talking to Hamas as unrealistic and said everyone knew Israel was negotiating with the organisation through an Egyptian mediator, Omar Suleiman. Suleiman took the Hamas ceasefire offer to Jerusalem last week.

Israel was still hesitating over the ceasefire, Carter confirmed yesterday. "I talked to Mr Suleiman the day before yesterday. I hope the Israelis will accept," he said.

While being scrupulously polite to the Palestinian Authority president, Mahmoud Abbas, and prime minister, Salam Fayyad, who represent the Fatah movement, he was scathing about their exclusion of Hamas. He described the Fatah-only government as a "subterfuge" aimed at getting round Hamas's election victory two years ago. "The top opinion pollster in Ramallah told me the other day that opinion on the West Bank is shifting to Hamas, because people believe Fatah has sold out to Israel and the US," he said.

Carter said the Quartet's policy of not talking to Hamas unless it recognised Israel and fulfilled two other conditions had been drafted by Elliot Abrams, an official in the national security council at the White House. He called Abrams "a very militant supporter of Israel". The ex-president, whose election-monitoring Carter Centre had just certified Hamas's election victory as free and fair, addressed the Quartet for 12 minutes at its session in London in 2006. He urged it to talk to Hamas, which had offered to form a unity government with Fatah, the losers.

"The Quartet's final document had been drafted in Washington in advance, and not a line was changed," he said.

Earlier, Carter, told Sky News that Hillary Clinton should abandon her battle to become Democratic presidential candidate after the last round of primaries in early June. Like many superdelegates, he has yet to declare his support for either Clinton or Barack Obama, but he suggested the outcome of the race was a foregone conclusion. "I think that a lot of us superdelegates will make a decision ... quite rapidly, after the final primary on June 3," he said. "I think at that point it will be time for her to give it up."

Last night, before a packed crowd at Hay, Carter spoke of his "horror" at America's involvement in torturing prisoners, saying he wanted the next US president to promise never to do so again.

He left an intriguing hint that George Bush might even face prosecution on war crimes charges once he left office.

When pressed by Philippe Sands QC on Bush's recent admission that he had authorised interrogation procedures widely seen as amounting to torture, Carter replied that he was sure Bush would be able to live a peaceful, "productive life - in our country".

Sands, an international legal expert, said afterwards that he understood that to be "clear confirmation" that while Bush would face no challenge in his own country, "what happened outside the country was another matter entirely".