Four major political parties on Friday signed a coalition agreement aimed at strengthening their positions in the legislature, party officials said.

The Golkar Party and the Indonesian Democratic Party of Struggle (PDI-P), the 2004 poll winners, entered a coalition that also included two upstart parties – the Great Indonesia Movement Party (Gerindra) and People's Conscience Party (Hanura) – believed to have been among the 10 largest vote getters in the April 9 legislative elections.

The coalition also involved four smaller parties that appear likely not to gain any seats from last month's elections.

But their self-proclaimed "jumbo coalition" agreement stipulated that the four main parties would initially only work together in the legislature at the national level, in the provinces, the districts and municipalities.

"We will talk about [the presidential candidate] later. We unite first, then we will decide on the technicalities. The coalition in the legislature is an initial step to set up a government," said Golkar chairman Jusuf Kalla after the signing at the Hanura party headquarters in Menteng, Central Jakarta.

The other signatories included PDI-P chairwoman Megawati Sukarnoputri, Gerindra founder Prabowo Subianto and Hanura chairman Wiranto.

The prospect of a coalition between the four was doubted by many who said it would be difficult for the parties to agree on a pair of candidates for the presidential and vice presidential elections on July 8.

Noticeably missing from the coalition were the United Development Party (PPP) and the National Mandate Party (PAN), which had earlier been touted as potential coalition members. Their respective chairmen, Suryadharma Ali and Sutrisno Bachir, were absent at the signing.

Suryadharma's deputy, Chozin Chumaidy, said the PPP had not signed the agreement, as the chairman was not mandated by his party to do so. Without the PPP and PAN, the coalition is believed to account for about 38 percent of the votes in the legislative elections. That may translate to about 40 percent of the 560 seats in the House of Representatives.

Bima Arya Nugraha, of the Charta Politika Indonesia private political consultancy, said the coalition could pose a real problem for the government. "This coalition has so much power if they become the opposition. They could be a problem for the government," he said.