Russia and China called on trade partner Iran on Tuesday to cooperate with the UN nuclear watchdog after the Vienna-based organisation accused Tehran of making its work more difficult by barring some inspectors.
Iran, which rejects Western accusations it is seeking to build atom bombs, said it was cooperating fully with the agency and had the right to reject UN inspectors which gave "false" information about its nuclear programme.
An International Atomic Energy Agency (IAEA) report, obtained by Reuters on Monday, said the Islamic Republic was pushing ahead with its nuclear work in defiance of tougher international sanctions.
It also voiced continued concern about possible activities in Iran to develop a nuclear-armed missile and called on Tehran to step up cooperation with the IAEA and give it access to relevant sites, equipment and personnel "without further delay."
Washington, which spearheaded a new wave of punitive measures imposed on the major oil producer since June, said the latest IAEA report was "troubling."
Russia and China, which have strong economic ties with Tehran and have at times resisted sanctions, both said Iran should improve cooperation with the Vienna-based IAEA.
Moscow and Beijing signed up to the latest round of UN sanctions, but did not support additional US and European measures that targeted Iran's oil and gas sector.
Russian Foreign Minister Sergei Lavrov said Iran needed to respond to the UN agency's demands.
"The IAEA must continue its work ... Iran must answer the demands of the IAEA," he told a news conference in Paris. His French counterpart Bernard Kouchner said "cooperation and collaboration was stopped by Iran."
In Beijing, Chinese Foreign Ministry spokeswoman Jiang Yu told reporters: "We hope that Iran and the agency can fully cooperate, and establish the trust of the international community in the peaceful nature of their nuclear plants."
She called for increased diplomatic efforts to seek a "long-term and appropriate resolution" to the nuclear dispute.
Iran is a major supplier of crude oil to China, the world's second-biggest consumer of oil after the United States.
The West hopes the new sanctions -- including measures that target the oil sector -- will persuade the Iranian leadership to back down and halt sensitive activity.
Iran has repeatedly rejected such demands and is sending mixed signals about its readiness to negotiate with the West.
Tehran has often dismissed the impact of sanctions and state television said on Tuesday Iran had raised gasoline production to attain self-sufficiency, a move that could make it less vulnerable to outside pressure.
The IAEA report voiced concern about what it called Iran's repeated objections to some inspectors, saying this hampered the inspection process.
Iran barred two inspectors from entering in June, accusing them of wrongly reporting that some nuclear equipment was missing. Iran also denied access to a senior inspector in 2006 and has objected to other appointments in the past.
Ali Akbar Salehi, head of Iran's Atomic Energy Organisation, said the inspectors who were rejected by Iran had reported false information, the ISNA news agency reported.
The IAEA has said it has full confidence in the professionalism and impartiality of the inspectors concerned.
Iranian officials have suggested that new IAEA chief Yukiya Amano is biased and has produced misleading reports.
The Japanese diplomat has taken a tougher approach on Iran than his predecessor Mohamed ElBaradei, with an IAEA report in February saying that Iran could be trying to develop a nuclear-armed missile.
Nicole Stracke of the Gulf Research Center in Dubai said the dispute over inspectors could "trigger an escalation" of the crisis between Iran and the international community.