UPDATE 3-Brent struggles to hold gains, US stockpiles weigh

* U.S. crude stocks jump more than expected - EIA

* Investors eye U.S. labour data due Thursday, Friday

LONDON Feb 2 (Reuters) - Brent crude oil struggled to sustain gains made earlier on Thursday as a large build-up of oil stocks in top consumer the United States countered upbeat economic data globally.

ICE Brent crude for March was up 9 cents to $111.65 a barrel by 1016 GMT after earlier rising as high as $112.50. U.S. crude was at $96.92, down 69 cents.

U.S. crude inventories jumped more than 4 million barrels last week, exceeding an expected build of 2.4 million barrels. Gasoline demand fell to an 11-year low.

But the outlook was not entirely gloomy.

Factory activity rose last month in the United States, China and Germany, the world's three manufacturing superpowers, raising hopes the global economy will not be dragged down by the euro zone debt crisis.

"We've got a bullish bias, and the Chinese PMI data was supportive of that," said Jonathan Barratt, chief executive of Barratt's Bulletin.

Investors are now eyeing employment data due from the United States for clues to the country's economic health.

IRAN SUPPLY WORRIES

U.S. lawmakers are considering a bid to force Washington to blacklist Iranian President Mahmoud Ahmadinejad and the country's supreme leader, Ayatollah Ali Khamenei, in an effort to thwart Tehran's nuclear capabilities.

Such a measure would designate them as human rights abusers, freeze any assets they have in the United States and deny them visas to enter the country.

The fresh penalties would build on a European Union oil embargo and sanctions by the United States that seek to shut out Iran's main clearinghouse for oil revenues, the Iranian central bank.

"It is a stalemate that will continue to squeeze Iran," Barratt said. "It's against everyone's interest to have a conflict as they don't want to see crude at $140 to $150."

The U.S. sanctions have put top crude buyers in Asia in a quandary. South Korea and Japan, heavily dependent on imports, will seek clarification from Washington on how much oil they can buy from Iran under the new law. (Additional reporting by Florence Tan in Singapore, editing by Jane Baird)