The United States reiterated on Thursday its willingness to hold bilateral talks with Iran later this month, hoping that Tehran would be ready to discuss "real substance" about its nuclear ambitions. "When Vice President Biden was in Munich he made clear that in the context of the P-5 plus one process, including the upcoming talks in Almaty, that we would be open to consulting with the Iranians bilaterally," said State Department spokesperson Victoria Nuland in a press briefing. "They have obviously got to make their own decisions how they want to proceed within the P-5 plus one context," she noted. Iran and world powers announced new round of talks on Iran's nuclear programs on February 26 in Kazakhstan. Nuland noted that the U.S. is "very much hoping that when we have this opportunity in a couple of weeks, that the Iranians will come prepared to discuss real substance." "Whether they prefer to do that with all of us in the room, whether they prefer to do that with all of us in the room and an opportunity to see us bilaterally, we are open to whatever can take this forward. What's most important is that they come prepared to really engage on the substance," she explained. "As the Iranians well know ,the ball is in the Iranians' own court. The burden of these sanctions could be eased if they made a decision to engage with us substantively. "We have always said that action on the Iranian side would be matched by action on our side. So it is really up to Iran to engage if it wants to see sanctions eased," she added. The Supreme leader of Iran, Ayatollah Ali Khamenei, rebuffed earlier today the U.S. offer for bilateral talks saying negotiations would not solve the problems between the two sides. "We have made an offer to engage. We have had three rounds of talks already. This will be the fourth one. We have been disappointed that those have not yet resulted in real, concrete progress. "We've also said that in the absence of progress, in the absence of movement, we would continue to ratchet up the international pressure. So as long as Iran fails to address the concerns of the international community, we are going to have to continue to increase the pressure and isolate Iran internationally". "This is really a choice that Iran's leaders can make. They can have a better path for their people, they can have a better path for their nation. But they have got to make the choice to come clean and answer the international community's concerns about their nuclear program, and that is yet to happen", she concluded.