Talks between Iran and six world powers continued Monday on the last day of their latest scheduled deadline, though two major issues threatened to force yet another extension.

Diplomats told reporters covering the talks in Vienna that removal of the U.N. arms embargo against Iran was a major sticking point. Iran is also insisting that any new U.N. resolution on its nuclear program be written to stop describing that program as illegal, the Associated Press reported.

"Talks have reached the final breathtaking moments; certain issues still remain," Iranian Deputy Foreign Minister Abbas Araqchi told reporters. "As long as these issues are not settled, one cannot say we have reached an agreement."

Monday is the latest deadline for an agreement set by Iran and the P5+1 countries — the United States, Britain, France, Germany, Russia and China. Though another extension could not be ruled out, negotiators from some countries indicated they were impatient for a resolution now that a deal is close.

"Conditions are already in place for us to reach a good agreement," Chinese Foreign Minister Wang Yi told reporters. "We believe that there cannot and should not be a further delay of the negotiations."

Iranian President Hassan Rouhani was standing by to address his nation on Monday night once an agreement was signed, the official Islamic Republic News Agency said.

Removal of the arms embargo, which Russia and China support, could be too high a price to pay for President Obama, who's already under fire even from Democrats for conceding too much in the talks. Both countries are eager to sell advanced weaponry to Tehran that could enable Iran's military to more effectively threaten U.S. forces in the Persian Gulf, along with Israel and U.S. allies in the Arab world.

"We have gone from preventing Iran having a nuclear ability to managing it," Sen. Bob Menendez of New Jersey, the president's leading Democratic critic on Iran, told ABC's "This Week" on Sunday.

Other key Democrats have described removal of the arms embargo as a deal-killer, a major headache for the administration as it counts votes in Congress for any potential action on a deal.

After being stonewalled for months by the White House on the talks, frustrated lawmakers overwhelmingly passed bipartisan legislation requiring Obama to submit any nuclear agreement with Iran for review to Congress, which must act within 60 days if a deal is submitted before Sept. 8, and 30 days after that.

During that period, Obama cannot exercise his authority under current law to waive existing U.S. sanctions enacted by Congress, though he retains full authority over any sanctions imposed by the executive branch. That limitation would become permanent only if Congress adopts a resolution of disapproval and is able to override an expected presidential veto.