The US State Department on Wednesday urged Iran to demonstrate its seriousness in nuclear talks with the European Union on its suspected nuclear weapons program.

"If Iran were really serious about demonstrating transparency in its nuclear program, it should answer all of the International Atomic Energy Agency(IAEA)'s outstanding questions.

"If Iran were really serious about allaying the concerns of the international community, they would stop denying IAEA full and unrestricted access to suspicious sites," deputy spokesman of the department Adam Ereli said at a news briefing.

Ereli called on Iran allow key nuclear officials to be interviewed by the IAEA and to come clean about its centrifuge program to enrich uranium as well as past efforts to extract plutonium as potential nuclear fuel.

The spokesman insisted that Washington and the EU-3, namely France, Germany and Britain, "remain united in the view that only a full cessation and dismantling of Iran's sensitive nuclear fuel cycle pursuits can provide the kind of confidence we're looking for that Iran has abandoned its nuclear weapons program."

The latest round of EU-Iran talks ended in Vienna last week with no signs of movement. The two sides decided to continue the talks in coming days.