One of the farms is owned and run by a church, a senior government-land official said on Monday.
"The minister of lands has signed the notices of expropriation and they have been sent. The owners have 30 days to respond, following which we will begin expropriation procedures," Tozi Gwanya, the chief land claims commissioner said.
Gwanya said one farm was located near the mining town of Cullinan, where the world's biggest diamonds are found, and the other is in the Northern Cape Province.
"The claimants to the Cullinan farm are two local families while the local African Pniel community are staking claim to the Northern Cape farm, which is owned by the Evangelical Lutheran Church of South Africa," he said.
Gwanya said negotiations in both cases had been dragging on for two years.
He said the state had offered $66,515 in compensation for the 106-hectare Cullinan farm, while the owner, OJ Botha, was demanding more.
"The more they delay, the more the land prices go up," he said, adding that the lands minister was in the process of finalising four more expropriation notices for four more white-owned farms in the northern Limpopo province.
The South African government has set itself a target of settling nearly 7,000 rural land claims before a December 2008 deadline.
The city of Pretoria is keen to finalise its lands claims and assure foreign investors it would not follow the same path as its neighbour Zimbabwe, which was plunged into crisis when farms belonging to white locals were seized and given to landless blacks.