The foreign ministers of the Sextet of world powers have been invited to join the ongoing talks on Iran's nuclear energy program in Vienna, Austria, a senior European Union official says.
EU's foreign policy chief, Catherine Ashton "has invited...foreign ministers who are available to come to Vienna on Sunday to take stock of where we are" in the negotiations on the Islamic Republic's nuclear energy program, Michael Mann, spokesman for Ashton, tweeted on Thursday.
Meanwhile, US State Department issued a statement, saying that US Secretary of State John Kerry will travel to the Austrian capital to join the negotiations between Iran and the six countries on Iran's nuclear energy program.
"The secretary will gauge the extent of Iran's willingness to commit to credible and verifiable steps that would back up its public statements about the peaceful nature of its nuclear program," State Department deputy spokeswoman, Marie Harf, said in the statement.
On Thursday, Russia expressed hope for a permanent accord on Iran's nuclear energy program, saying it sees signs of progress in the ongoing talks between Tehran and the world powers.
"The discussions are quite difficult, but there are clear signs of progress," Russian Foreign Ministry spokesman, Alexander Lukashevich, said.
On July 3, Iran and the five permanent members of the United Nations Security Council -- the United States, France, Britain, Russia and China -- plus Germany formally kicked off their sixth round of nuclear talks this year to discuss a permanent accord on Tehran's nuclear energy program.
Iran and the six countries have been discussing ways to iron out differences and achieve a final deal. The two sides sealed an interim deal in the Swiss city of Geneva on November 23, 2013. The deal came into force in January and will expire on July 20, but it can be extended depending on an agreement by all the parties to talks.