Hassan Rouhani is now officially the president of Iran

Hassan Rouhani, the man swept into office on a wave of optimism, officially starts his term as Iranian president on Saturday.

Irianians elected Rouhani to replace outgoing President Mahmoud Ahmadinejad in June.

He won the support of the country's reform movement and has promised to open up the country and end its international isolation.

The formal inauguration for Rouhani will be held Sunday, where his election will be endorsed by the country's Supreme Leader Ayatollah Ali Khamenei.

Rouhani will have a tough uphill battle once the inaugural festivities are over.

The new Scottish-educated president is tasked with resolving Iran's long-standing nuclear dispute and easing tough economic sanctions.

Inflation under Ahmadinejad soared by 40 percent and Iran's currency has lost about half its value since mid-2012.

Unemployment among Iran's young people stands at about 1 in 4, even for the country's 4 million university graduates.

"Before the election, everyone was saying anyone, anyone at all, has to be better than Ahmadinejad," one Tehran resident told Reuters.

"Now people hope Rouhani might be able to change things, at least a bit."

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One central challenge for Rouhani will be that the country's Supreme Leader has veto power over virtually any decision the president makes.

In the Islamic Republic, it is the Supreme Leader — not the president — who will be Iran's final decision maker and has the last word, the BBC said.

Rouhani has a lot of experience working with the Ayatollah Ali Khamenei.

He comes to the presidency after spending 16 years as the head of the Supreme National Security Council and the last eight years as one of two personal representatives of the Supreme Leader on the same body.

Despite being an Islamic Republic insider, Rouhani has still signaled that he's ready to move forward.

"Of course our nuclear plans are fully transparent, but we are ready to show more transparency," said Rouhani at his first post-election news conference. "Second, we will increase mutual trust between Iran and other countries."

The US House of Representatives was not sold by Rouhani's statements and passed a bill on Wednesday calling for tougher sanctions against Iran

The bill would cut Iran's oil exports by another 1 million barrels per day over a year to nearly zero in order to stop the flow of money into its nuclear program.

House members passed the bill 400-20 despite a commitment from the White House to give Rouhani a chance.