DUBAI - Iran's Supreme Leader Ayatollah Ali Khamenei said on Monday he was not optimistic about upcoming nuclear talks with world powers but was not opposed to them, the official news agency IRNA reported.Iran and world powers, grouped under the so-called "5+1," reached an interim deal last November whereby Tehran agreed to suspend for six months parts of its nuclear enrichment operations in return for modest sanctions relief. The two sides hope to build on those gains in Tuesday's talks in Vienna."I have said before ... I am not optimistic about the negotiations. It will not lead anywhere, but I am not opposed either," Khamenei told a large crowd during a visit to the northwestern Iranian city of Tabriz, according to IRNA."What our foreign ministry and officials have started will continue and Iran will not violate its (pledge) ... but I say again that this is of no use and will not lead anywhere."Khamenei's comments came as the Iranian ambassador to Moscow said in remarks published on Monday that Russia could build a second reactor at Iran's Bushehr nuclear power plant in exchange for Iranian oil.Reuters reported last month that Iran and Russia were negotiating to swap up to 500,000 barrels of oil per day for goods in a deal that would undermine Western efforts to maintain economic pressure on Tehran while global powers seek to curb its nuclear program."Iran could use some of the proceeds (to pay for) the construction by Russian companies of a second unit at the nuclear power plant in Bushehr," ambassador Mehdi Sanaei told the daily Kommersant. Russia built the first reactor at Bushehr, Iran's sole nuclear power plant.