Based on communications with Harris, in April 2014, Bahn and Ban Ki-sang agreed to pay an upfront $500,000 bribe and another $2 million upon the sale's closing to an official at the Middle Eastern country's sovereign wealth fund, the indictment said. Ban has called the report ill-founded and threatened to take legal action against the magazine.
Ban told reporters on Wednesday in NY that he was surprised by the accusations.
The country has been rocked by an influence-peddling scandal involving impeached President Park Geun-hye and her friend Choi Soon-sil.
It remains unclear whether Ban will join Park's ruling Saenuri Party or the emerging conservative party.
But opposition parties stressed the need to thoroughly check Ban's qualifications to be a presidential candidate. The man who served as head of the United Nations in the last decade is the favorite for South Korea's presidential candidate in an election that will take place later this year, although they could be earlier if it is finally decided to make Park Geun-hye to step down, surrounded by a corruption scandal and influence peddling. In December, he stepped down as UN Secretary General after a 10-year tenure in the post.
"And then, I will, with a humble heart, make a decision without any pursuit of personal gains".
A career diplomat, Ban never joined any South Korean political party, although he served as foreign minister under the late liberal president Roh Moo-hyun from 2004 to 2006.
Analysts told Singapore newspaper The Straits Times that Ban might offer a public apology to minimise the impact of the scandals on his presidential bid.
Asked to comment on a clause in a 1946 United Nations resolution, which some say forbids a former United Nations chief from running for an elected office, Ban said that it does not keep him from engaging in political activities.
He said it was urgent for South Korea to draw up countermeasures to resolve the Democratic People's Republic of Korea (DPRK)'s nuclear issue and solidify relations with the countries, including the United States, China, Russia and Japan.
In 2016, South Korea witnessed the biggest anti-government protests seen in decades. The court is expected to make a decision before June.
If the constitutional court upholds the parliamentary vote, Park will be permanently removed and elections held within 60 days.