Iran, world powers finally reach nuclear deal

Iranian Foreign Minister Mohammad Javad Zarif arrives for the final plenary meeting at the United Nations building in Vienna, Austria. After 18 days of intense and often fractious negotiation, diplomats Tuesday declared that world powers and Iran had struck a landmark deal to curb Iran's nuclear program in exchange for billions of dollars in relief from international sanctions.

From left to right: European Union High Representative Federica Mogherini, Iranian Foreign Minister Mohammad Javad Zarif, Head of the Iranian Atomic Energy Organization Ali Akbar Salehi, Russian Foreign Minister Sergey Lavrov, British Foreign Secretary Philip Hammond and US Secretary of State John Kerry pose for a group picture at the United Nations building in Vienna, Austria.

French Foreign Minister Laurent Fabius, right, German Minister for Foreign Affairs Frank-Walter Steinmeier, left, and US Secretary of State John Kerry, center, talk prior to their final plenary meeting at the United Nations building in Vienna, Austria.

US Secretary of State John Kerry, right, Russian Foreign Minister Sergey Lavrov, center, and China's Foreign Minister Wang Yi arrive for their final plenary meeting at the United Nations building in Vienna, Austria.

President Barack Obama, standing with Vice President Joe Biden, delivers remarks in the East Room of the White House in Washington, after an Iran nuclear deal is reached. Obama heralded a historic nuclear agreement with Iran Tuesday as an opportunity for the longtime foes to move in a “new direction,” while sharply warning Congress that it would be irresponsible to block the accord.

German Foreign Minister Frank-Walter Steinmeier (L), French Foreign Minister Laurent Fabius (2nd L), Chinese Foreign Minister Wang Yi (3rd L), European Union foreign policy chief Federica Mogherini (Centre in red), U.S. Secretary of State John Kerry (4th R) and Russian Foreign Minister Sergei Lavrov (R) meet at a hotel in Vienna.

Palais Coburg, the venue for nuclear talks, is seen behind a street sign in Vienna, Austria.

US Secretary of State John Kerry attends a plenary session at the United Nations building in Vienna, Austria.