Kerry: 'Tough issues' remain for Iran nuke deal

Oren Dorell | USA TODAY

Show Caption Hide Caption John Kerry insists Iran negotiation talks are 'not open-ended' John Kerry has said nuclear negotiations in Vienna would continue past a congressional deadline on Thursday night, insisting that they could not be rushed. The US secretary of state was speaking a few hours before a deadline set by the US Congress.

Secretary of State John Kerry said Thursday "tough issues remain unresolved" in talks to curb Iran's nuclear program, and the United States is prepared to walk away if they're not settled.

"We believe we are making real progress toward a comprehensive deal," Kerry told reporters in Vienna, where the talks are taking place. "But... we are not going to sit at the negotiating table forever."

World powers – the United States, Britain, France, Russia, China and Germany – have been seeking an agreement by Friday to limit Iran's nuclear program in return for lifting U.S. and international sanctions that have crippled Iran's economy. The U.S. goal in the talks is to prevent Iran from producing a nuclear weapon, which Iran says it does not seek.

"If, in the end, we are to reach a deal, it has to be one that stands the test of time … a test for decades," Kerry said, adding he would not be rushed to reach a deal.

Many members of Congress skeptical of making a deal with Iran have urged the Obama administration not to be bound by deadlines and to focus on getting a good agreement.

White House spokesman Josh Earnest said the effort will last as long there is progress.

If "there does not seem to be a constructive engagement on the part of the Iranians to resolving the remaining sticking points in the negotiations, then the president won't hesitate to bring his team home," Earnest said.

The deadline for the current round of talks was extended from June 30 to Tuesday and then to Friday. Many differences were resolved, but the talks snagged on two sensitive issues. The first is the sequence of lifting sanctions and whether they could be easily restored if Iran doesn't comply with its obligations. The second is whether sanctions relief would include international arms embargoes on Iran.

Each deadline extension also continued the conditions agreed to in November 2013 that required Iran to limit its nuclear activities while talks are ongoing.

In April, the sides announced a general framework for a final deal that would require what President Obama said would be unprecedented scrutiny of Iran's nuclear program. It also called for restrictions for 10 to 15 years on how much nuclear fuel Iran could produce.

Iran, which would commit to keep its program peaceful, says it needs a very large nuclear fuel enrichment capability to supply current and future nuclear power plants. Many members of Congress and Israel worry that could provide Iran the means to supply a secret nuclear weapon.

On Sunday, Kerry said the sides had agreed on much, but that remaining differences were so important they could nix the deal. "If there's absolute intransigence, if there's an unwillingness to move on the things that are important, President Obama has always said we'll be prepared to walk away," Kerry said. "It's not what anybody wants. We want to get an agreement."

Contributing: David Jackson