John Solecki was serving as the head of the U.N. refugee office in Quetta, and the U.N. is still trying to make contact with the kidnappers who have threatened to kill their captive.
The kidnapping has underlined the overall deteriorating security situation in nuclear-armed Pakistan, which is battling al-Qaida and Taliban-led militants in its northwest. In her message, Rose Solecki expressed bewilderment at her son's predicament.
"I simply do not understand why this is happening to our dear John," said Rose Solecki, 83. "I cannot begin to explain the sorrows and pain that I am going through right now. My husband and I are old. We want to be with John again. We cannot bear losing John."
The audio message was released through the United Nations along with a photo of Solecki and his parents.
The U.N. has said the matter is very urgent because Solecki has a medical condition. In a 20-second clip released by his kidnappers on Feb. 13, a blindfolded Solecki said he was "sick and in trouble."
Rose Solecki noted that she and her 91-year-old husband Ralph are both archaeologists and that she had lived in Baluchistan many years before. The couple visited their son in the provincial capital of Quetta last year, she said.
"This recent happy memory quickly turned into a nightmare," she said. "To our friends in Baluchistan, please help us find John and have him returned safely to his family, friends and colleagues. John has helped many people in Baluchistan, and now my son needs your help."
In the Feb. 13 message, Solecki's captors threatened to kill him within 72 hours, but later said they would extend the deadline for a "few days." It was unclear exactly when the new deadline would expire.
The kidnappers have identified themselves as the previously unknown Baluchistan Liberation United Front. The name indicates the group is more likely linked to separatists than to Islamists. The kidnappers have demanded the release of 141 women allegedly held in Pakistan, but Pakistani officials have said no such group of women are being held.
Earlier Saturday, a suspected Shiite gunmen killed two members of the rival Sunni Muslim sect in the northwest city of Dera Ismail Khan, police said, a day after a suicide bombing at a Shiite leader's funeral killed 36 and set off sectarian riots.
Three other Sunnis were wounded Saturday when the gunmen rode by a market on a motorbike and fired, area police chief Miran Shah said.