President Obama prepared to fight for historic Iran deal

US president Barack Obama faces stormy weeks ahead as he must convince fellow Democrats and Republicans at home and disgruntled allies in the Middle East about the merits of a landmark nuclear deal with Iran.

Vowing to veto any Republican attempt to derail the agreement in the US Congress, Mr Obama warned that without the deal there would be “a greater chance of more war in the Middle East”.

Capping 12 years of negotiations, six world powers reached a deal with Iran that limits their nuclear activity, preventing Tehran from building an atomic bomb, in return for lifting economic sanctions.

"Every pathway to a nuclear weapon is cut off," said Mr Obama in an early-morning address from the White House broadcast live in Iran and one of a series of carefully choreographed events.

After 18 consecutive days of talks and four missed deadlines in Vienna, Mr Obama heralded the deal as "real and meaningful change" that makes the United States and the world "safer and more secure".

New chapter

Iranian president

Hassan Rouhani

said the “historic” deal opened a “new chapter” in Tehran’s relations with the world following the talks with the US, UK,

France

,

Russia

,

China

and

Germany

. The Iranian people’s “prayers have come true”, he said.

Under the deal, the international community would be able to verify Iran is not building a nuclear bomb through unprecedented checks by inspectors “where necessary, when necessary”, said Mr Obama.

“This deal is not built on trust – it is built on verification,” he said.