NEW YORK (Reuters) - Bitfinex Chief Strategy Officer Phil Potter is leaving the cryptocurrency trading platform, the executive and the exchange told Reuters on Friday.

FILE PHOTO: Photo illustration of Bitfinex cryptocurrency exchange website taken September 27, 2017. REUTERS/Dado Ruvic/Illustration

Potter will be replaced in the interim by Chief Executive JL van der Velde, the company said.

“As Bitfinex pivots away from the U.S., I felt that, as a U.S. person, it was time for me to rethink my position as a member of the executive team,” Potter said in a statement.

He referred to “new opportunities” in the days ahead but did not elaborate.

Owned by a British Virgin Islands company, Bitfinex is the fourth-largest cryptocurrency exchange in the world by trading volume. It enables traders to buy and sell virtual currencies such as bitcoin and ether.

The exchange shares management with Tether, a company that issues a cryptocurrency that is pegged to the U.S. dollar.

Tether critics have raised concerns over the past year about whether it actually holds $1 in reserve for every token issued, as it claimed.

Earlier this month a University of Texas research paper alleged Tether’s token could have been used to manipulate bitcoin’s price last year during its meteoric rise.

Bitfinex has denied these claims.

This week a Washington-based law firm co-founded by former FBI director Louis J. Freeh said in a report released by Tether the company had enough U.S. dollar reserves as of June 1 to back its virtual coins in circulation. The report was not a full audit.

Global regulators have ramped up their scrutiny of cryptocurrency markets following a rally in prices last year. The U.S. Commodity Futures Trading Commission and the Department of Justice are reportedly investigating whether the price of bitcoin is being manipulated.

In December the CFTC sent a subpoena to Tether and Bitfinex.

Potter, an American who once worked at Morgan Stanley, was one of three main Bitfinex managers, including the CEO and a chief financial officer based in Europe.