The U.S. government has asked South Korea to arrest a brother of former U.N. Secretary-General Ban Ki-moon on charges that he engaged in a bribery scheme to carry out the sale of a Vietnamese building complex, a U.S. prosecutor said on Friday.

During a court hearing in federal court in Manhattan, Assistant U.S. Attorney Daniel Noble said that a request had been made for the arrest of Ban Ki-sang, who was an executive at South Korean construction firm Keangnam Enterprises Co Ltd.

Noble said the United States plans to seek his extradition, "but as of yet, he has not been apprehended."

South Korea's Justice Ministry was discussing the request to arrest Ban but "it is not yet a formal consultation," Yonhap news agency quoted an unnamed source in the country's judiciary as saying.

Officials at the Justice Ministry could not be reached for comment. An official at the foreign affairs section of the national police said the agency had yet to receive a formal request to arrest Ban and declined to give further details.

Ban Ki-sang could not be reached for comment. An official at Keangnam said Ban had left the company in March 2015 and it was not aware of his whereabouts.

Ban Ki-sang was one of four people charged on Jan. 10 in a case that has complicated his brother's expected run for president of South Korea following his recently finished term at the United Nations, informs Reuters.

The case has already resulted in the arrest of another of the former U.N. chief's relatives, Joo Hyun "Dennis" Bahn, a real estate broker living in New Jersey who is Ban Ki-moon's nephew and Ban Ki-sang's son.

Ban Ki-moon, who is ranked second in opinion polls among potential candidates for South Korean president, issued an apology on Saturday in Seoul and said he hoped any cooperation between authorities in South Korea and the United States would be "strict and transparent."