The United States has warned of “serious gaps” in negotiating positions at the Iran nuclear talks in Vienna. European officials also voiced doubts an agreement would be in place by the end of the weekend. CCTV’s Jack Barton had the report from Vienna, Austria.

As Monday’s deadline for an agreement on Iran’s nuclear program  approaches, U.S. Secretary of State John Kerry warned that deep divisions remain.

“We’ve been obviously having difficult talks here on a complicated topic,” said Secretary Kerry. “We’re working hard. We hope we’re making careful progress, but we have big gaps.”

Despite the impasse, German Foreign Minister Frank Walter Steinmeir remained upbeat.

“Now in our 10 years negotiations about Iran, this is the weekend, or these are the hours of truth and we have to check now if Iran is really ready to move in the right direction,” said Steinmeir.

Negotiators still hope for an agreement setting strict limits on Tehran’s nuclear program in a bid to slow Iran’s ability to produce nuclear weapons. Iran insists its nuclear program is only for energy and research and is negotiating for an end to international sanctions that have crippled its economy.

Even so, Iran wants further concessions than those currently being offered. A deal involving further concessions would be harder for U.S. President Barack Obama to sell to a skeptical U.S. Congress set to be controlled by the Republican Party.

On Saturday, European officials reportedly warned the chances of an agreement by the set deadline were slim, fueling expectations of yet another extension to the talks.