Russian President Dmitri Medvedev says Iran will provide convincing proof about its peaceful intentions with its nuclear programme at a meeting of the six big powers in Geneva next Thursday.Medvedev said the revelations that Iran has a second nuclear facility it has been keeping secret are a cause for serious concern. “The Sextet is due to meet with Iranian representatives on the 1st of October. This is an Iranian opportunity to confirm its adherence to the negotiations. That is possible if Iran is ready to concentrate on the nuclear problem at the Geneva meeting, to take practical steps in building up confidence in its nuclear programme and its transparency, and to display the readyness for large-scale cooperation with the IAEA,” he said. News of the secret facility was made public by US President Barack Obama during the G-20 summit. “I have said repeatedly that we’re going to operate on two tracks, that our preferred method of action is diplomatic, but that if that does not work, then other consequences may follow,” he said. Western countries fear Iran is working to make nuclear weapons. Teheran insists its nuclear programme is designed solely to generate electricity. Obama and Medvedev agreed on Wednesday that serious additional sanctions had to be considered if Iran did not respond to proposals to end the nuclear standoff.