Representatives of Iran and six world powers are meeting in Geneva to discuss the implementation of their nuclear deal. But officials say differences could delay enactment.

Before the two-day meeting, European Union spokeswoman Maja Kocijanic said Thursday "some issues remain to be resolved," a statement echoed by Iranian officials.

They gave no details. But two officials say Iran wants to continue enriching uranium to 20 percent at one facility — something opposed by the six powers that signed the Nov. 24 deal with Tehran.

The officials are from member countries of the U.N. nuclear agency. They demanded anonymity because they are not authorized to discuss the closed negotiations.

Uranium at 20 percent can be quickly turned into nuclear weapons-grade material. Iran says it is enriching only to make reactor fuel.