WASHINGTON, Feb. 8 (Xinhua) -- U.S. Secretary of State John Kerry on Friday called on Iran to talk "real substance" with the world powers over its disputed nuclear program, saying the "window for diplomacy" is still open.
The top American envoy made the appeal as Iran has agreed to start fresh talks with the so-called P5+1 group of Britain, China, France, Russia, the United States and Germany on Feb. 26 in Kazakhstan.
"I want to underscore to Iran. The window for diplomacy is still open," he told reporters after meeting with his Canadian counterpart John Baird at the State Department. "And we will continue our dual-track policy of both pressure and engagement."
"The international community is ready to respond if Iran comes prepared to talk real substance and to address the concerns which could not be more clear about their nuclear program," Kerry said.
"If they don't, then they will choose to leave themselves more isolated," he added, reiterating Washington's commitment to prevent Iran from securing a nuclear weapon.
For his part, Baird called a nuclear-armed Iran the "biggest threat to international peace and security."
Iran's Supreme Leader Ayatollah Ali Khamenei on Thursday ruled out direct bilateral talks with Washington, as offered by U.S. Vice President Joe Biden last week, on the grounds that the Obama administration has shown "ill-will" by imposing "paralyzing sanctions to paralyze the Iranian nation."
Iran insists on the peaceful nature of its nuclear program, while the West regards it as a cover for making nuclear bombs.
Iran and the six powers held three rounds of talks last year but made no breakthrough.
In its latest effort to add more pressure on Iran, the Obama administration on Wednesday tightened up economic sanctions against the Islamic republic and adding more names to its blacklist.