Oil major Royal Dutch Shell has stopped gasoline sales to Iran, oil traders said on Wednesday, the latest addition to a growing list of firms that have halted supplies under threat of future U.S. sanctions.

The Anglo-Dutch oil firm will join the likes of BP, Reliance Industries, and independent Swiss trader Glencore, among suppliers that have either stopped fuel sales to Iran or have made a decision not to enter into new trading agreements with the world's fifth largest oil exporter.

Shell has stopped selling gasoline to Iran, we have not seen them there for a while now, a gasoline trader said.

A Shell spokesman said: Shell currently does not supply gasoline to Iran.

Vitol, one of the world's largest independent oil traders, said earlier this week it had decided to stop participating in new tenders to supply Iran with gasoline at the start of the year.

But the Swiss-based firm said it was completing existing spot supply deals that were made before the start of the year. The Financial Times reported on Monday that Trafigura had also stopped supplying gasoline to Iran.

U.S. politicians are working on legislation to penalize fuel suppliers to Iran in an effort to pressure Tehran to stop uranium enrichment.

The west says the Islamic Republic is using its atomic program to develop nuclear weapons, while Iran insists that it is for nuclear electricity.

It is getting more difficult for suppliers, who are only stopping this because it is politically sensitive, a trading source familiar with Iranian fuel imports said.

DELIVERIES

Shipping data obtained by Reuters showed that Shell moved a total of about 1.65 million barrels of gasoline into Iran from April through October 2009.

Despite the pull back by international oil companies and large independent trading firms, Iran has still managed to find supply sources for its monthly gasoline requirements.

It is going to be harder but Iran will still find a way to bring in the gasoline, a trader said. And as long as there is money to be made someone is going to sell the gasoline to them.

France's Total,, Malaysia's state oil firm Petronas and Kuwait's Independent Petroleum Group are among firms that continue to ship fuel to Iran, traders said.

Iran is the world's fifth-largest oil exporter but lacks adequate refining capacity to meet domestic demand for the motor fuel, forcing it to import up to 40 percent of requirements.

The country spends billions of dollars annually to plug its shortfall through imports from the international spot market and then subsidizing the gasoline at the pump.

Iran has also introduced a rationing scheme to curb consumption.

On Tuesday, Iran's parliament blocked President Mahmoud Ahmadinejad's plan to phase out subsidies on food and energy by approving only half of the savings requested by the government.

Iran's purchases of gasoline from abroad for February were about 23 percent higher than the 2009 average, at more than 150,000 bpd, Reuters data showed.

(Reporting by Luke Pachymuthu; editing by Keiron Henderson)