The Iraqi government announced a rationing system for gasoline and engine oil Friday, citing shortages of chemical additives because of the U.N. blockade imposed to force President Saddam Hussein's troops out of Kuwait.

The measure, in a country with huge oil reserves and a major petroleum industry, was the clearest indication to date of economic disruption caused by the economic embargo authorized by the U.N. Security Council after Iraq seized Kuwait on Aug. 2.Baghdad motorists and taxi drivers immediately formed lines at service stations, seeking to fill their tanks before the rationing system is put into effect. An announcement from the Oil Ministry said rationing cards for private cars, taxis and trucks should be picked up beginning Saturday at distribution centers listed in the press and that the cards are necessary to buy gasoline or oil beginning Tuesday.

Basic foodstuffs - including tea, bread, rice and milk - have been rationed since early last month. But the addition of gasoline was expected to have a particular impact here and abroad because petroleum is the symbol of Iraq's rise as a modern economic power, accounting for 90 percent of government revenues before the Persian Gulf crisis.

Apparently with the local reaction in mind, the government announced the measure on Friday, the Moslem day of prayer and rest, when commercial activity was at its lowest, and the ordinary rush of traffic slowed to a weekend pace. Abroad, however, the step is likely to be read as a sign the embargo has begun to take hold in Iraqi industry, which diplomats here have said is the key target.

Although gasoline has remained plentiful at a government-set price equivalent to slightly more than $1 a gallon at the official exchange rate, engine oil has been scarce for the last several weeks, with prices climbing steadily and taxi drivers lining up at distribution points to buy supplies.

Oil Minister Issam Abdul-Rahim Chalabi said that although exports have been blocked, Iraq is pumping enough oil to meet domestic consumption of between 300,000 and 400,000 barrels a day.

"The only reason for this (rationing) is to guarantee that we will have the additives and chemicals that we require to continue making these products," he told reporters. "We are only rationing gasoline and lubricants because they depend on additives that we have to get from the outside."