Secretary of State John Kerry believes it would be a "mistake" for the US Congress to impose additional sanctions on Iran now amid negotiations with Tehran over its nuclear programme, a State Department spokeswoman said.

Jen Psaki said Kerry, who will hold a closed-door briefing on Iran at the Senate Banking Committee on Wednesday, wants a "temporary pause" in the imposition of additional sanctions on Tehran by US lawmakers to give diplomacy a chance.

Iran and six world powers - the US, Britain, Russia, France, China and Germany - came close to a preliminary nuclear agreement at the weekend during talks in Geneva and decided to resume negotiations on November 20 in their attempt to defuse a decade-old standoff.

Israel and some Western governments fear Iran is using its nuclear programme as a covert means to develop weapons, a charge that Tehran denies.

Negotiators are searching for a preliminary agreement that would cap Iran's nuclear capacity and open up the programme to UN inspectors.

In exchange, they have offered some relief from sanctions, a concession Iran says does not go far enough.

Under discussion is a temporary deal entailing a freeze to higher-grade uranium enrichment - which Iran bills as fuel for a medical research reactor but which is also potential material for bombs - lasting about six months.

During that time, Iran and the six powers would negotiate a permanent agreement aimed at ensuring that none of Iran's nuclear activities could be diverted towards bomb-making.

Source: Agencies