The United Nations has formally invited Iran to join the long-awaited Syrian peace talks, which are scheduled to open Wednesday in Switzerland.
Secretary-General Ban Ki-moon told reporters Sunday that he believes Iran "needs to be a part of the solution in Syria," and that Foreign Minister Javad Zarif assured him Iran understands the basis of the talks.
"Foreign Minister Zarif and I agreed that the goal of the negotiations is to establish by mutual consent a transitional governing body with full objective powers. It was on that basis that Foreign Minister Zarif pledged that Iran would play a positive and constructive role in Montreux," said Ban.
Iran has long rejected that goal, set at a 2012 international peace conference, because a transitional authority would likely exclude Syrian President and major Iranian ally Bashar al-Assad.
The main opposition Syrian National Coalition does not want Iran to take part in the talks, and said on Twitter it would withdraw unless Ban retracts Iran's invitation.
U.S. State Department spokeswoman Jen Psaki said the United States remains "deeply concerned" about Iran's support of Assad's government, and that Iran must publicly accept the peace conference's goals or be uninvited from the talks.
Assad told the French News Agency in an interview published Monday that the conference must focus on terrorism, and that his forces are fighting an extremist group, not a popular uprising.
The Syrian government has routinely classified opposition fighters as terrorists throughout the nearly three-year-old crisis.
AFP quoted Assad as saying some of the opposition groups set to attend the conference were "created" by intelligence agencies in Qatar, Saudi Arabia, France and the United States. Each of those nations is a member of the so-called Friends of Syria, which has supported the opposition.
Assad also said there is a "significant" chance he will run again for president, and that he will not hesitate to do so if the public supports his candidacy.
Ban has also invited nine other nations that have an interest in the Syrian civil war to join the talks. He said their presence would be an important show of solidarity.
The U.N. chief also welcomed the main opposition group's decision, now called into question, to attend.
The Syrian government said the issue of Assad giving up power is not up for discussion, so few experts expect the talks will reach this goal. However, they say they do hope the discussions will result in increased humanitarian access and local cease-fires to make life easier for Syrian civilians.