"Europe has made a step in the right direction in making Tehran, under threat of sanction, accept tighter controls of its nuclear installations," the official said.
"But international pressure must be constant as Iran wants to gain time and fool the world in regard to its intentions," he said.
The official is part of a delegation accompanying Israeli Prime Minister Ariel Sharon on a three-day visit to Russia, and on Monday was due to meet with Russian President Vladimir Putin.
Russia is building Iran's first nuclear power reactor at Bushehr, which has been fiercely criticized by Washington and Israel.
Israel hopes that Russia "is doing everything possible to prevent the transfer of technologies on uranium enrichment and fusion that are indispensable for developing a nuclear program that constitutes a strategic menace for Israel," the Israeli delegation official said.
Iran, which has been branded by US President George W. Bush part of an "axis of evil" along with Iraq and North Korea, has faced growing international criticism in regard to its nuclear program.
In September the International Atomic Energy Agency (IAEA) imposed an October 31 deadline on Iran to fully disclose details of its nuclear program and urged it to sign the additional protocol to the nuclear Non-Proliferation Treaty (NPT) allowing tougher inspections by the UN watchdog.
Iran was also urged to suspend uranium enrichment.
After initially rejecting the deadline, Iran agreed to comply with IAEA demands just 10 days before the deadline expired during an unprecedented joint visit by British, French and German foreign ministers.
Iran has also pledged to sign up to tougher inspections, but has yet to implement its agreement to suspend its work on the nuclear fuel cycle.
And on Sunday, it said that it remained unwilling to totally halt uranium enrichment.
"Our uranium enrichment activities are still in their early stages, and it has only been several months since we began. We have said we agree to voluntarily suspend this, but not stop," foreign ministry spokesman Hamid Reza Asefi told reporters.