Britain denied on Wednesday that negotiations were under way towards a new round of nuclear talks between Iran and Western powers, contradicting Iran's foreign minister Ali Akbar Salehi.
"There are no dates or concrete plans because Iran has yet to demonstrate clearly that it is willing to respond to (EU foreign policy chief) Baroness Ashton's letter and negotiate without preconditions," a spokesman for the Foreign Office in London said.
"Until it does so, the international community will only increase pressure on it through further peaceful and legitimate sanctions," he said.
The sanctions, targeting Iran's oil exports in an attempt to halt what Western governments say is its effort to develop nuclear weapons, would bar financial institutions from the American market if they do business with Iran's central bank.
Tehran claims the reactors are for civilian energy use and scientific research.
Edited by: S. Isayev