The White House warned staff against improperly leveraging their positions to place bets in futures markets in an email on March 24, a day after President Donald Trump ordered a brief pause in some Iran strikes, a White House official said on Thursday.

Some of Trump's major policy decisions have been preceded by well-timed bets, leading some experts to question whether information had somehow leaked ahead of time.

Exchange data and Reuters calculations showed an unidentified trader or traders bet $500 million on Brent and WTI crude futures in a one-minute period shortly before Trump called a five-day delay on March 23 in attacks on Iran's energy infrastructure, after which oil prices crashed 15%.

"While he (Trump) seeks a strong and profitable stock market for everyone, members of Congress and other government officials should be prohibited from using nonpublic information for financial benefit," White House spokesman Davis Ingle told Reuters in a statement.

The Journal, which previously reported the news, said the announcement was made in a staff-wide email from the White House management office.