WASHINGTON (CNN) — Iranian nuclear negotiations are getting increasingly difficult as diplomats stare down a fast-approaching deadline at the end of the month — a deadline officials said may need to be extended.

A senior U.S. official and Western diplomat downplayed a report from the Russian news agency Tass, which quoted a diplomat as saying talks are “virtually stalled.” The two officials instead told CNN Friday that negotiations are tough, as expected, but continue to move forward.

But the two sources said that the talks are at a delicate moment and that negotiations may have to be extended a few days past the June 30 deadline. Nobody in the room is yet talking about a full-scale extension, they added.

The United States and five other world powers are negotiating with Iran to curb the country’s nuclear program and keep it from building a nuclear bomb. Iran has insisted that its nuclear program is peaceful, and in April the parties reached a framework to hash out the details of a final deal.

Sanctions relief for Iran and the level of access inspectors will have in that country continue to be major sticking points in the negotiations.

Iran wants near immediate sanctions relief, while Western officials are wary of lifting sanctions too quickly as they keep an eye on Iran’s activities in the early months after a deal is reached.

Western diplomats are also pushing for unprecedented levels of access that would allow international inspectors to visit any facility in Iran suspected of nuclear activity, including military sites. Tehran has strongly pushed back on that level of access, looking to keep military sites off limits.

World powers also want Iran to come clean about any past efforts to develop a military dimension to its nuclear program. Although it seems unlikely that that issue will be fully resolved before any deal is reached, U.S. officials and European diplomats insist sanctions relief will be tied to Iran satisfying lingering questions from the International Atomic Energy Agency, the UN nuclear watchdog.

One incentive the sides have to reach an agreement by the deadline or shortly thereafter: An extremely skeptical Congress will have 30 days to review a final nuclear deal with Iran — a period that will be doubled if a deal isn’t reached by July 9.

The-CNN-Wire ™ & © 2015 Cable News Network, Inc., a Time Warner Company. All rights reserved. (PHOTO: CNN)