Hurdles stack up

As uncertainty persists over talks aimed at ending the 12-year standoff on Iran's disputed atomic programme, hurdles to an agreement are stacking up.

In Washington, lawmakers are considering imposing new sanctions on Tehran despite calls from the White House to give the negotiations more time.

Hardline Iranian MPs have responded with threats of their own and are drafting two bills that would undermine the talks.

With the going already tough -- the level of uranium enrichment Iran can conduct and a timetable for lifting sanctions are said to be blocking a deal -- analysts say pressure is being ratcheted up.

In the Iranian capital, officials say the United States and other world powers need to show more flexibility in nailing down the hard details of a deal.

Iran's negotiators have given no indication a compromise is in the offing and supreme leader Ayatollah Ali Khamenei, who has the final word, last month voiced doubt that the US could be trusted.

Israel is lobbying hard against a final deal and Saudi Arabia is also wary, analysts say, and the negotiations could be scuttled if there is no definitive progress soon.

The biggest threat, they say, is the possibility of new US sanctions on Iran, which Foreign Minister Mohammad Javad Zarif has said would effectively "torpedo" the talks.

Two US senators, Republican Mark Kirk and Democrat Robert Menendez, have said they will decide by March 24 whether to table new legislation.

In Tehran, MPs are considering two bills, one tearing up an interim deal that has reined in Tehran's nuclear activities and another allowing the Islamic republic's atomic scientists to speed up their operations.