"Of course the more clearly Iran states its intention to sign the additional protocol, the happier we are," the spokeswoman for EU External Affairs Commissioner Chris Patten said.
"We believe it is in Iran's own interest as well as in the interests of the international community. We would like to see the deeds as well as the words with this issue as well as the suspension of Iranian enrichment," Emma Udwin told reporters.
"What we would most like to see is implementation of the very welcome announcement that Iran has made."
Tehran's representative to the UN nuclear watchdog, the International Atomic Energy Agency (IAEA), on Monday handed in a letter pledging Iran would sign an additional protocol to the Nuclear Non-Proliferation Treaty (NPT) to allow wider and suprise inspections.
Ali Akbar Salehi also told IAEA head Mohammed ElBaradei that Iran was suspending its enrichment program.
The United States has repeatedly accused Iran of secretly trying to make atomic weapons, charges Tehran strongly denies.