MS Jayasinghe, secretary of the reconstruction ministry, signed the pact on behalf of the government, and Norwegian peace brokers then took the document north to the rebel-held capital of Kilinochchi for the Tigers to sign, according to a top official involved in the signing.
The official said he could not be quoted by name ahead of a formal announcement of the accord later Friday.
Sri Lanka's influential Buddhist clergy, a powerful Marxist party and other key critics say the deal raises the rebels' legitimacy in the international community, boosting their separatist agenda and undermining Sri Lanka's sovereignty.
The Marxists pulled their 39 lawmakers out of President Chandrika Kumaratunga's ruling coalition over the issue, reducing the coalition to a precarious 81-seat minority in the 225-member Parliament.
The government could collapse if other parties side with the Marxists in a no-confidence vote.
The eight-page Post-Tsunami Operational Management Structure, a copy of which was obtained by The Associated Press, says the body will be made up of a three-tiered system of committees to review and approve projects in the Tamil-majority north and east.
The parties are "resolved to work together in good faith and using their best efforts to deliver expeditious relief rehabilitation, reconstruction and development," the document said. The body aims to "facilitate and expedite the process of rebuilding the affected areas."
A representative from the government,
International donors had urged the parties to sign the deal, as many countries are reluctant to give the rebels money directly since they are branded as terrorists in many nations.
The signing Friday came despite protests by hundreds of Marxist demonstrators who marched near Parliament to demand that the aid-sharing plan be dropped. Police fired tear gas to disperse them, and two protesters were injured. More protests followed in front of the city's port and at two universities.
The aid-sharing pact was presented to the legislature for debate after months of secrecy, and raucous protests by Marxist politicians prompted legislative leaders to suspend the parliamentary session until July 5.
However, the accord does not need legislative approval.
Kumaratunga has promoted the plan as a golden opportunity for the government to forge peace with the guerrillas as the country recovers from the Dec. 26 tsunami, which struck both government and rebel-held areas and killed at least 31,000 people.
The rebels say areas under their control have been overlooked in reconstruction efforts and have demanded more say in how international donations for Sri Lankans are spent.
A 2002 cease-fire halted the nearly two-decade civil war between the Tigers and the government that left nearly 65,000 people dead. Subsequent peace talks have deadlocked.