The former general came to power after an abortive coup on September 30, 1965, officially blamed on the communist party.
Suharto was charged with embezzling hundreds of millions of dollars of state funds after he quit office, but the government later dropped the case due to his poor health. He and his family deny any wrongdoing.
Transparency International put Suharto's assets at $15-$35 billion (7.6-17.8 billion pounds), or as much as 1.3 percent of gross domestic product.
Since his admission to hospital, a "who's who" of Indonesia's elite - family members, ministers, and military men - as well as several long-serving Asian leaders have dropped by his bedside to pay their respects.
Suharto's friend and contemporary Lee Kuan Yew called at the hospital in south Jakarta at the weekend.
Lee, 84, now Singapore's Minister Mentor, was prime minister for decades at the same time as Suharto's rule in Indonesia. He told Singapore media he felt Suharto was not getting the honour he deserved.
On Monday, the 82-year-old former prime minister of Malaysia, Mahathir Mohamad, prayed and whispered into Suharto's ear during his visit. Brunei's Sultan Hassanal Bolkiah has also visited Suharto, who was forced out of office by mass protests in 1998.
Doctors said on Tuesday that Suharto had taken a turn for the worse.
Hermansyur Kartowisastro, one of the doctors treating Suharto, said he was suffering from pneumonia in one of his lungs, while another said the former president was developing blood poisoning.
"It is clearly heading towards sepsis. There has been a decline in (his) digestive functions," Djoko Rahardjo of his medical team told reporters at a news conference.
Medical team chief Mardjo Soebiandono said on Sunday there was only a 50-50 chance he could survive.
