In Qatar, Mrs Clinton will address the annual US-Islamic World Forum and meet Turkish premier Recep Tayyip Erdogan, whose country opposes the sanctions. US Secretary of State Hillary Clinton has arrived in the Gulf to rally Arab support for tougher sanctions against Iran over its nuclear programme.
The three-day tour will include her first ever trip to Saudi Arabia. The Obama administration is stepping up pressure on Iran by launching a diplomatic offensive in the Gulf.
Washington wants the UN Security Council to impose a fourth round of sanctions on Tehran.
Iran says its nuclear programme is to generate electricity so it can export more of its valuable oil and gas, but the West suspects it of trying to develop atomic weapons.