"My zeal, my love of Israel, and my concern for the future safety of your nation led me to make remarks which I can now view in retrospect as inappropriate and insensitive in light of a national grief experience because of your father's illness," Robertson wrote to Omri Sharon.
"I ask your forgiveness and the forgiveness of the people of Israel for saying what was clearly insensitive at the time."
Robertson wrote to Sharon's son on the same day that Israel's tourism ministry said it no longer would do business with the televangelist. Last Thursday, Robertson said God was punishing Sharon for "dividing God's land," a reference to last summer's pullout from the Gaza Strip and four West Bank settlements.
In his letter, Robertson told Sharon's son that "I expressed on television my sadness at [Sharon's] condition and my warm regard for him as a person.... To me, he is a kind, gracious, and gentle man. He was carrying an almost insurmountable burden of making decisions for his nation.
"Regrettably, few, if any, of those heartfelt sentiments were carried by the news media in America or by the news media in Israel. However, I ask your forgiveness and the forgiveness of the people of Israel for remarks I made at the time concerning the writing of the holy prophet Joel and his view of the inviolate nature of the land of Israel."
Robertson is leading a group of evangelicals who have pledged to raise $50 million to build a large Christian tourism center in Israel's northern Galilee region, where tradition says Jesus lived and taught.
Avi Hartuv, a spokesman for Tourism Minister Avraham Hirschson, said on Wednesday that Israeli officials were furious with Robertson's comment that Sharon's stroke was divine retribution. "We can't accept this kind of statement," Hartuv said.
He said the Christian Heritage Center project was now in question, though he left the door open to develop it with others.
"We will not do business with him, only with other evangelicals who don't back these comments," Hartuv said. "We will do business with other evangelical leaders, friends of Israel, but not with him."
"Those that publicly support Ariel Sharon's recovery ... are welcome to do business with us."
The Associated Press contributed to this report.