U.S. Secretary of State John Kerry said Monday that "significant points of disagreement" remain in international negotiations to prevent Iran from acquiring nuclear weapons as the high-stakes talks were extended for another seven months.
   
The United States, four other permanent members of the U.N. Security Council, and Germany failed to meet a Monday deadline for a deal with Tehran on the nuclear issue and decided to extend the so-called "P5-plus-one" negotiations until July next year.
   
It was the second time the talks have been extended after the first extension in July this year.
   
The extension underlined the difficulty to get Iran, one of the countries branded with Iraq and North Korea as an "axis of evil" by former U.S. President George W. Bush, to forswear its nuclear ambitions. Negotiations over North Korea's nuclear program have been stalled for nearly six years.
   

"These talks aren't going to suddenly get easier just because we extend them. They're tough and they've been tough and they're going to stay tough," Kerry told reporters in Vienna, according to a transcript provided by the State Department.    

"Now we believe a comprehensive deal that addresses the world's concerns is possible. It is desirable. And at this point, we have developed a clearer understanding of what that kind of deal could look like, but there are still some significant points of disagreement, and they have to be worked through," he said.
  
The six world powers -- Britain, China, France, Russia, the U.S. and Germany -- have tried to reach a nuclear deal with Iran since 2006. The negotiations are aimed at curbing Iran's nuclear activity in exchange for relief from international sanctions.
  
Iran claims its nuclear program is for peaceful purposes only. (Yonhap)