Indonesia's vice president has said accommodating a key Aceh rebel demand finalising a peace agreement will require a constitutional amendment.
One of Gam's key demands was local political participation
At the end of a meeting in Finland on Sunday, the two sides agreed a draft deal to end the 29-year insurgency.
The government and rebels from the Free Aceh Movement (Gam) had agreed to sign the truce at a ceremony on 15 August.
But questions remain over the issue of political representation, which has proved a sticking point throughout.
During talks earlier in the week Gam abandoned its demand for Acehnese independence in return for a certain amount of autonomy and greater access to the region's rich natural resources, and both sides agreed to establish an Aceh monitoring mission, overseen by experts from European Union and other Asian countries.
ACEH: ESSENTIAL FACTS
Located on the northern tip of Sumatra island
Population of 4.3m people
Rich fuel resources, including oil and natural gas
Gam rebels have been fighting for an independent state
But the main difficulty has been the rebels' request for participation in local Acehnese politics.
It appears the government may have acquiesced to this demand, but is still unclear whether the accord will allow Gam to form its own Aceh-based party - and if so, when.
"A local party would need a change in the law, that would need the agreement of the parliament," Mr Kalla told reporters in Jakarta on Sunday.
"The government will try as hard as it can to create the political and legal situation in support of that."
Under current legislation, every political party in Indonesia must have representation in at least half of the country's 33 provinces, and have its headquarters in Jakarta.
Analysts say that any exception to that rule could lead to demands from other separatist groups elsewhere in Indonesia, which some Indonesian officials - especially among the military - fear could spark further attempts at secession from Jakarta.
In Aceh itself - where more than 120,000 people died in the 26 December tsunami - opinions on the peace deal are divided.
"I hope that both sides will respect this agreement," said Dian, one of many Acehnese who lost several family members in the tsunami.
15,000 people have been killed in three decades of conflict
"All we want here is to live peacefully and free, to go anywhere we want and be able to express our opinions," she told the Associated Press.
But others remembered that the last peace deal, brokered in late 2002, fell apart soon afterwards with each side blaming the other for not sticking to the agreement.
"All this is only promises, just like the promises from previous negotiations," newspaper agent Joni Sukandar told Reuters news agency on Monday.
About 15,000 people have died in the 29-year conflict between the government and Gam rebels.