* U.S. considers tapping emergency stockpiles to lower prices
* U.S. crude rallies almost $2/bbl, closes in on Brent
* Clerics forbid protests in top exporter Saudi Arabia
* Coming Up: ECB's Trichet presser; 1130 GMT (Recasts with concerns about Saudi Arabia in first paragraph)
By Alejandro Barbajosa
SINGAPORE, March 7 (Reuters) - U.S. crude rose to a 2-1/2-year high on Monday as civil war brewed in Libya, while investors kept a close eye on top exporter Saudi Arabia, home to most of OPEC's spare capacity, where clerics forbid protests at the weekend.
U.S. crude for April rose as much as $1.90 to $106.32 a barrel, the highest price since September 2008, adding to concerns that high energy prices may derail the global economic recovery. It was up $1.76 at $106.18 at 0351 GMT.
This year's 16 percent rally in U.S. crude has prompted the Obama administration to consider releasing emergency oil stockpiles as policymakers seek ways to contain a negative spillover to the world's biggest economy.
"The concern is that with what we are seeing in Libya, it's purely fear driving the market," said Jonathan Barratt, managing director at Commodity Broking Services in Sydney.
Saudi Arabia has pledged to fill any supply gap caused by the disruption of exports from Libya. The kingdom is pumping around 9 million bpd and has spare capacity of around 3.5 million bpd, a senior Saudi source told Reuters last week.
But Saudi Shi'ites last week staged small demonstrations in the Eastern Province, which holds much of the kingdom's oil wealth, leading clerics to ban protests.
"Each time the price moves up a little, people are forced into the market. Once it's feeding itself, it will continue to rise," Barratt said, adding $120 may be the peak without further supply disruptions.
ICE Brent crude for April gained $1.27 to $117.24, still more than $2 away from the contract's peak this year at $119.79 on Feb. 24. Its premium over U.S. benchmark West Texas Intermediate (WTI) has narrowed to about $11 from more than $15 last week.
Saudi security forces have detained at least 22 minority Shi'ites who protested last week against discrimination, activists said on Sunday, as the kingdom tried to keep the wave of Arab unrest outside its borders.
The kingdom's Eastern Province is near Bahrain, the scene of protests in recent weeks by majority Shi'ites against their Sunni rulers. More than 17,000 people backed a call on Facebook to hold two demonstrations in Saudi Arabia this month, the first one this coming Friday.
EMERGENCY STOCKPILES
U.S. unemployment in the U.S. fell to near a two-year low in February, jobs data showed on Friday, but a surge of 23 percent in Brent prices this year threatens that positive turnaround. Oil prices may slip back to more "realistic" levels around $80 later this year, Barratt said.
White House Chief of Staff William Daley said on Sunday the U.S. was considering tapping into the strategic petroleum reserve (SPR) as a way to lower prices, adding that "a bunch of factors have to be looked at," not just prices.
High prices also threaten Asian economies. "At $120 a barrel, we estimate oil prices to shave off 1.5 percentage point from baseline growth" for Asia excluding Japan, RBS economists Sanjay Mathur and Erik Lueth said.
Japan and South Korea, among the world's top 5 crude oil importers, have no immediate plans to release oil from strategic reserves to fill any shortfall left by the unrest in Libya, industry and government officials said.
News about the potential use of U.S. emergency oil stocks failed to dampen prices as investors remained jittery that the unrest in oil-producing nations of the Mideast Gulf may escalate and affect crude production there.
"It doesn't matter what they say because it's fear," Barratt said, referring to the Obama administration's possible use of the SPR. "We have ample supplies after OPEC, led by Saudi Arabia, stepped in."
In Libya, troops loyal to Gaddafi launched counter-offensives against rebel-held towns on Sunday backed by tanks, artillery, warplanes and helicopters, attacking positions near the rebel-controlled oil port of Ras Lanuf, 660 km (410 miles) east of the capital.
Gaddafi has lost control to rebels of most of the country's east, the main oil producing region in the OPEC member nation. Many oil facilities are idle or working at well below capacity.
Oil sources said refining operations and exports of crude by firms operating in the town, including units or ventures with the state-owned National Oil Corp (NOC), had ground to a halt over previous days because of the unrest and supply problems.
Rebels now hold an area west of Ras Lanuf that includes al-Sidrah, the last major oil terminal town in the east of the country. That would mean rebels now have all the main oil terminals in the east of Libya in their hands.
Libya usually produces 1.6 million bpd, but output has been slashed by as much as 1 million bpd, according to the International Energy Agency.
Emergency strategic oil reserves held by the International Energy Agency member nations are equivalent to almost three years of Libyan crude output, highlighting the ability of some of the world's largest energy users to compensate for disruptions to supply over extended periods. (Editing by Himani Sarkar)