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(CNN) -- World leaders have welcomed the historic peace deal struck Monday between the Indonesian government and separatist rebels in Aceh province, but fears remain the pact may prove short-lived.
Rebel leaders are concerned pro-government militias armed by the Indonesian military may disrupt the peace deal. A government spokesman told CNN Tuesday such issues would not threaten the new accord.
Foreign Ministry spokesman Marty Natalegawa said the presence of third-party monitoring forces in Aceh and the "strong determination" by both sides to implement the agreement would quell those worries.
Monitoring troops will be provided by the European Union and ASEAN.
"We are confident ... we can overcome those kinds of concerns," he said.
Indonesian President Susilo Bambang Yudhoyono later rejected nationalist criticism that his government was giving foreigners too big a role in the peace agreement, Reuters news service reports.
"The conflict in Aceh is a domestic issue. We never intended to internationalize it," Yudhoyono said in a speech prepared for delivery to parliament ahead of Indonesia's August 17 independence day.
"The presence of foreign monitors from the European Union and ASEAN to monitor the implementation of the Memorandum of Understanding is not a foreign interference into our domestic affair," he said, according to Reuters.
Aceh has suffered nearly 30 years of often savage internal violence resulting in 15,000 deaths as independence fighters sought autonomy from Jakarta's control and access to the revenue generated by the province's energy resources.
But when the December 26 earthquake and tsunami struck, killing as many as 130,000 people, it acted as a catalyst for renewed peace negotiations.
Crucially, the Free Aceh Movement -- Gerakan Aceh Merdeka, or GAM -- gave up their previously unconditional demand for full independence from Jakarta, settling instead for limited autonomy -- including the right for GAM members to contest local and national elections.
In return, Jakarta granted the province 70 percent of revenue from the region's rich oil and gas resources and the ability to levy local taxes.
Jakarta also will reduce the number of troops in the region gradually from the current 30,000 to nearer to 9,000. Separatist fighters have been granted an amnesty.
Natalegawa said the key difference in this peace deal was the commitment of both sides to work within the same framework.
"It allows GAM to work within the national political system," he said, adding that local concerns could now be addressed through proper channels rather than through violence.
The peace deal was signed in Finland Monday by Indonesian Justice and Human Rights Minister Hamid Awaluddin and by Malik Mahmud, an exiled rebel leader who was briefly jailed in Sweden last.
Former Finnish President Ahtisaari, who mediated the seven months of peace talks, called the accord the "beginning of a new era for Aceh."
"Much hard work lies ahead. It is of utmost importance that the parties honor the commitments they have made in the agreement," he said after the signing.
Rebel leader Mahmud however voiced concern over the number of Indonesian troops that would remain in the province saying it "does not appear to correspond with the usual requirements of the Indonesian military's territorial structure."
"At the end of this process there will be around twice as many troops to be stationed in Aceh as any other area in Indonesia," he said, adding that such a presence did not "inspire confidence" in the intentions of the Indonesian military.
International reaction to the deal, however, has been positive.
"We commend both parties for their vision and courage to seek lasting peace for the people of Aceh," U.S. State Department spokesman Sean McCormack said in a statement.
"The United States commends the European Union and five member countries of the Association of Southeast Asian Nations for their willingness to participate in the monitoring of the implementation of the Memorandum of Understanding," McCormack said.
"We look forward to supporting the implementation of the peace agreement in the coming months."
Near neighbor Australia also offered its support for the pact.
"The agreement offers real opportunity for lasting peace for the people of Aceh, still rebuilding their lives after the devastating Indian Ocean tsunami," Foreign Minister Alexander Downer said in a statement.
"I am pleased all parties were able to put aside their differences and negotiate a peaceful resolution within a framework that respects Indonesia's sovereignty and territorial integrity."
Canadian Foreign Affairs Minister Pierre Pettigrew expressed similar sentiments.
"We fully support this process and hope that this memorandum of understanding between the government of Indonesia and the Free Aceh Movement will result in lasting peace in Aceh," he said Monday.