Diplomats with the United Nations nuclear agency say they will hold talks in Tehranlater this month on allegations that Iran is secretly building a nuclear weapon.

Iran has always denied the charge, insisting its nuclear program is strictly peaceful. It has refused to directly talk about the issue with Western negotiators.

The European Union is planning an Iranian oil embargo. Iran says it would respond by shutting down vital Persian Gulf oil shipping lanes — something the United States says it will not let happen.

Iran is seething with anger over Wednesday's assassination of a top-ranking nuclear scientist in Tehran. Iran blames the United States and Israel and is demanding the U.N. Security Council condemn the murder. An editorial in Iran's Kayhan newspaper called for assassinations of Israeli military and other officials.

Israel and the United States deny involvement. But U.S. Defense Secretary Leon Panetta said Thursday U.S. officials have some ideas who may be responsible.

Iranian media say two men on a motorcycle attached a bomb to a car, killing nuclear scientist Mostafa Ahmadi Roshan. Roshan was a supervisor at the Natanz nuclear facility, Iran's main uranium enrichment site.

Attackers have killed or wounded several Iranian nuclear scientists in recent years, including blasts in late 2010 that state media also attributed to bombs placed on cars by motorcyclists.