The UN general assembly has overwhelmingly approved a resolution calling on Israel to open its nuclear programme for inspection.

The resolution, approved by a vote of 174 to six with six abstentions, calls on Israel to join the Nuclear Nonproliferation Treaty (NPT) "without further delay" and open its nuclear facilities to inspection by the International Atomic Energy Agency. Those voting against were Israel, the US, Canada, Marshall Islands, Micronesia and Palau.

Resolutions adopted by the 193-member general assembly are not legally binding but they do reflect world opinion and carry moral and political weight. And the resolution adds to pressure on Israel as it faces criticism over plans to increase settlement in the West Bank, a move seen as retaliation for the assembly recognising Palestinian statehood.

Israel refuses to confirm or deny possessing nuclear bombs though it is widely believed to have them. It has refused to join the non-proliferation treaty along with three nuclear weapon states: India, Pakistan and North Korea.

Israel insists there must first be a Middle East peace agreement before the establishment of a proposed regional zone free of weapons of mass destruction. Its rivals in the region argue that Israel's undeclared nuclear arsenal presents the greatest threat to peace in the region.

While the US voted against the resolution, it voted in favour of two paragraphs in it that were put to separate votes. Both support universal adherence to the NPT and call on those countries that aren't parties to ratify it "at the earliest date". The only no votes on those paragraphs were Israel and India.

The vote came as a sequel to the cancellation of a high-level conference aimed at banning nuclear weapons from the Middle East. All the Arab nations and Iran had planned to attend the summit in mid-December in Helsinki, Finland, but the US announced on 23 November that it would not take place, citing political turmoil in the region and Iran's defiant stance on non-proliferation. Iran and some Arab nations countered that the real reason for the cancellation was Israel's refusal to attend.

Just before Monday's vote, the Iranian diplomat Khodadad Seifi told the assembly "the truth is that the Israeli regime is the only party which rejected to conditions for a conference". He called for "strong pressure on that regime to participate in the conference without any preconditions".

Israeli diplomat Isi Yanouka told the general assembly his country had continuously pointed to the danger of nuclear proliferation in the Middle East, singling out Iran and Syria by name. "All these cases challenge Israel's security and cast a dark shadow at the prospect of embarking on a meaningful regional security process," he said.

"The fact that the sponsors include in this anti-Israeli resolution language referring to the 2012 conference proves above all the ill intent of the Arab states with regard to this conference."

The Syrian diplomat Abdullah Hallak told the assembly his government was angry the conference was not going to take place because of "the whim of just one party, a party with nuclear warheads".

"We call on the international community to put pressure on Israel to accept the NPT, get rid of its arsenal and delivery systems, in order to allow for peace and stability in our region," he said.

The conference's main sponsors are the US, Russia and Britain. The British foreign office minister Alistair Burt has said it is being postponed, not cancelled.