David Cameron's landmark phone call to Iranian president Hassan Rohani has once again raised expectations surrounding the nuclear talks between Iran and world powers in Geneva.

Cameron has become the first British prime minister to call an Iranian leader in more than a decade, according to Downing Street.

Apart from the latest developments on bilateral ties between the two countries, the leaders discussed Iran's nuclear issue. Both of them are said to have agreed that "significant progress" has been made during the previous rounds of the Geneva talks.

A No 10 spokesperson said: "The two leaders discussed the bilateral relationship between Britain and Iran, welcoming the steps taken since President Rouhani took office, including the appointment of non-resident charges d'affaires last week. They agreed to continue efforts to improve the relationship on a step by step and reciprocal basis."

The spokesperson added: "On Iran's nuclear programme, both leaders agreed that significant progress had been made in the recent Geneva negotiations and that it was important to seize the opportunity presented by the further round of talks which get under way on Wednesday.

"The prime minister underlined the necessity of Iran comprehensively addressing the concerns of the international community about their nuclear programme, including the need for greater transparency."

Rohani wrote on his Twitter account that he discussed with Cameron a ways to create a positive atmosphere to address concerns on both sides on the nuclear issue".

Cameron's telephone call has come just hours ahead of the next round of talks between Iran and the P5+1 powers comprising Britain, China, France, Russia, Germany, and the US.

In a further sign of the softening of the western stand on Iran, President Barack Obama has told US senators to step back from suggesting more sanctions against Iran in order to pave the way for progress on the nuclear deal.

The British premier's latest gesture has also come on the heels of Russian President Vladimir Putin's phone conversation with Rohani.

Britain has recently shown great interest in renewing its ties with Iran, especially following moderate cleric Rohani's takeover as president.

Earlier this month, both nations named non-resident charges d'affaires to each other's capital, a significant step forward in the diplomatic ties between the countries.

The UK's relationship with Iran collapsed when protesters ransacked the British embassy in Tehran in 2011, leading to the closure of the diplomatic post. The Iranian embassy in London was also later shut down.