"Together, we are encouraging Iran to reconsider its dangerous policy decisions," Clinton said in a speech at the US-Islamic World forum in Doha.
Clinton, on a visit to the Gulf, is seeking to enlist more Arab diplomatic pressure on Iran to curb its nuclear ambitions and to win greater Arab support to revive frozen Israel-Palestinian peace talks, US officials said.
"We are now working actively with our regional and international partners, in the context of our dual track approach, to prepare and implement new measures to convince Iran to change its course," Clinton added.
"Iran has consistently failed to live up to its responsibility. It has refused to demonstrate to the international community that its nuclear program is entirely peaceful," she said.
The chief US diplomat said US endorsement of an offer to provide Iran with fuel for the Tehran Research Reactor "demonstrated good-faith commitment to working with Iran" toward a peaceful civil nuclear program. But she scolded Tehran for refusing the terms of the International Atomic Energy Agency. "This has only deepened the international community's doubts about Iran's nuclear intentions, along with the Iranian government's own isolation," she said.
Clinton said Washington was "disappointed" with the lack of a breakthrough in the Middle East peace process, but stressed solutions cannot be forced. "I know people are disappointed that we have not yet achieved a breakthrough. The president, Sen. (George) Mitchell, and I are also disappointed. But we need to remember that neither the United States nor any country can force a solution. The parties must resolve their differences through negotiations," she added.
Clinton flew in to Qatar on Sunday on the first leg of her Gulf tour. On Monday, she will visit Saudi Arabia, where she will hold talks with Custodian of the Two Holy Mosques King Abdullah.
"Clinton is scheduled to arrive in Riyadh on Monday afternoon before proceeding to Jeddah after meeting King Abdullah," said a Foreign Ministry spokesman. Their talks will focus on a range of bilateral, regional and international issues of common concerns, said the spokesman. "In her first visit to Saudi Arabia as secretary of state, Clinton will also hold talks with Foreign Minister Prince Saud Al-Faisal," he added.
US President Barack Obama has made little headway in his effort to restart peace talks or persuade Iran to rein in a civil nuclear program which the West suspects is a cover to develop atomic weapons.
