The sons of a pastor who was jailed in China for illegally crossing the border are hoping that the government would consider reducing the sentence of their father in light of his charitable works in the country.

The Rev. John Sanqiang Cao was arrested on March 5, 2017 when he crossed the China-Myanmar border on his way back to Yunnan province. Last month, he was sentenced to seven years in prison for "organizing others to illegally cross the border."

The pastor has established more than a dozen Bible schools in China and he had been crossing with fellow Christian teachers into Myanmar to provide free education to ethnic Burmese children.

Ben Cao, one of the pastor's sons living in the U.S., said he believes that the sentence against his father was harsh considering his humanitarian work.

"Nothing my father organized was ever political. It was always just religious or charitable," Cao told the Associated Press (AP). "We hope that China will be merciful, and see that my father's intentions were good," he added.

According to China Aid, Cao married an American woman named Jamie Powell and became a resident of North Carolina. But the pastor retained his Chinese citizenship and still flies back to his home country from time to time to work on humanitarian projects.

Ben Cao contended that his father always tried to obtain the permission of the authorities for his work. The pastor did not hesitate to turn over a primary school and health clinic that he established to the authorities and did not resist when he was ordered to stop some of his charitable work.

Despite his willingness to cooperate with the authorities, Cao has been put under constant surveillance and is regularly questioned about his work.

According to Christian rights activist Bob Fu, Cao was frequently summoned by the authorities over his recruitment of Chinese volunteers for the construction of schools in Myanmar's Wa state.

"There were no secrets. He always believed that he operated with the government's tacit blessing," Fu said, as reported by AP.

A U.S. State Department spokesman has called on the Chinese government to release Cao on "humanitarian grounds," noting that the pastor intends to retire and return to the U.S. after he is freed.

Cao's sentencing came after China implemented new religious regulations in February this year. According to the AP, the new regulations include a provision that prohibits Chinese nationals from leaving the country for religious purposes without permission from the government. Those who are found to be in violation of the regulation could be fined up to 200,000 yuan ($31,780).