PHNOM PENH, Cambodia (AP) _ A court controlled by Cambodian strongman Hun Sen convicted his ousted co-premier in absentia today of trying to overthrow the government. The court sentenced the deposed leader to 30 years in prison.

Today's proceedings _ which also saw the conviction of an aide who has been dead for eight months _ were the first step in an elaborate, internationally brokered deal to clear the way for the return of the former co-premier, Prince Norodom Ranariddh.

Ranariddh has been in exile since Hun Sen seized sole power in a bloody July coup, ending their coalition government.

Today's trial was both an attempt by Hun Sen to discredit his former colleague and part of a diplomatic effort to allow Ranariddh to return to Cambodia to contest elections July 26.

But diplomats feared that an unexpected $54 million fine leveled by the judge against Ranariddh could become a stumbling block to the prince's return.

Ranariddh's office in Bangkok, Thailand, called the proceedings a ``judicial farce ... in the best Stalinist tradition.''

Ranariddh's conviction was a foregone conclusion in the Hun Sen-controlled military court, which also sentenced three of the prince's aides, all in absentia.

The prince has denied all the charges, which alleged he conspired with Cambodia's Khmer Rouge guerrillas against Hun Sen, and called the proceedings illegal.

The proceedings are part a Japanese-brokered settlement aimed at saving face on both sides. It outlines a plan whereby Ranariddh would seek a royal pardon from his father, King Norodom Sihanouk, paving the way for his return to Cambodia.

But the pardon _ and the prince's return _ still is very much up in the air.

Vibol Kong, the prince's deputy Cabinet director, said in Bangkok, Thailand, that Ranariddh's sister, Princess Buppha Devi, was preparing an amnesty request on behalf of the prince.

Ranariddh has refused to seek the pardon himself, saying it would amount to an admission of guilt. Sihanouk, meanwhile, says he will grant the amnesty only if Hun Sen says in writing he would favor it. Hun Sen has been ambivalent.

Hun Sen has called the elections to legitimize his power and win back foreign aid that was cut off after his takeover. The international community has indicated the prince's return and participation are necessary components for free and fair elections.

Today's trial concluded shortly after convening for the second day at a heavily guarded lecture hall at the Defense Ministry.

A series of witnesses, including Ranariddh's former military adviser, testified Tuesday that the prince was plotting to oust the more powerful Hun Sen by enlisting the aid of Khmer Rouge guerrillas.

``Ranariddh is surely guilty,'' said Nhey Thol, the judge. ``Ranariddh wanted to seize the power. These activities cannot be forgiven.''

The proceedings had many of the characteristics of a show trial. For starters, a dead man _ Ranariddh aide Chao Sambath, killed by Hun Sen's troops during the coup_ was among those sentenced today.

Also, the court fined the four defendants $54 million for damages to businesses caused by looting during the coup _ even though the pillaging was done by Hun Sen's soldiers.

It was unclear whether the pardon scheme takes the fine into account.

Ranariddh's top military commander, Gen. Nhek Bunchhay, and a former security adviser, Serey Kosal, were sentenced to 20 years in prison.