The countries would also insist Iran accept strict controls on its nuclear activities, said a western diplomatic source, who added that senior representatives of the countries had arrived in Tehran in recent days to "resolve this crisis peacefully."
His remarks followed a pledge earlier in the day by Tehran, during a quick visit to the Iranian capital by the International Atomic Energy Agency (IAEA) head, Muhammad El Baradei, to accelerate cooperation with the UN nuclear watchdog.
The Islamic republic, just two weeks away from an IAEA deadline to prove it is not developing atomic weapons, also said it may even bow to demands for tougher UN inspections.
According to the diplomatic source, the German, French and British envoys met during the day with ElBaradei.
They were hoping to help convince Iran to accept the IAEA demands, which include opening all its nuclear sites to inspection and full disclosure of its nuclear programme, especially answering questions about enriching uranium which could be used to make atomic weapons.
These countries "may favourably consider the possibility of supplying (Iran) with technology, even nuclear technology, as well as nuclear fuel"
Unnamed western diplomat
El Baradei said earlier that Iran had not yet indicated from which countries it had imported the equipment Tehran claims is the source of highly enriched uranium particles discovered by IAEA inspectors.
Washington contends that these particles do not come from contaminated equipment from abroad but are in fact proof that Iran is making highly-enriched uranium.
The IAEA has also been pressing Iran to sign the additional protocol to the nuclear Non-Proliferation Treaty (NPT), which would give the watchdog the right to carry out unannounced inspections of suspect facilities.
If Tehran accepts all the IAEA demands, "these countries" - Germany, France and Britain - "may favourably consider the possibility of supplying (Iran) with technology, even nuclear technology, as well as nuclear fuel," the source said.
He said that a tripartite ministerial-level mission from the western countries was also shortly expected to visit Iran.