Vienna, November 21 (RHC)-- Negotiations over Iran’s nuclear energy program entered their fourth day in the Austrian capital, Vienna, as a November 24th deadline to reach a final accord is approaching.

Iran’s Foreign Minister and top nuclear negotiator Mohammad Javad Zarif, U.S. Secretary of State John Kerry and EU representative Catherine Ashton sat down for the second round of a trilateral meeting on Tehran’s nuclear program on Friday.

The meeting is part of the negotiations between Iran and the P5+1 group of world powers -- the U.S., Britain, France, Russia, China and Germany -- to work out a final deal aimed at ending the longstanding standoff over the Islamic Republic’s nuclear energy program.

Iran and the six powers started the final round of talks before the November 24th deadline. Sources close to the Iranian negotiating team say the main stumbling block in the way of resolving the Western dispute over Iran’s nuclear energy program remains to be the removal of all the bans imposed on the country, and not the number of centrifuges or the level of uranium enrichment.

Tehran wants the sanctions entirely lifted while Washington, under pressure from the pro-Israeli lobby, insists that at least the UN-imposed sanctions should remain in place.