US oil futures hit their highest in over a month on Thursday as a potential hurricane threatened crude output in the Gulf of Mexico and as an incident involving a British tanker in the Middle East highlighted ongoing tensions there.
US West Texas Intermediate (WTI) crude futures were up 11 cents at $60.54 a barrel by 0055 GMT, after earlier touching the highest since May 23 at $60.63. They gained 4.5% in the previous session.
Brent crude futures were down 5 cents, or 0.1%, at $66.96 a barrel, after ending Wednesday up 4.4%.
Five boats believed to belong to Iranian Revolutionary Guards approached a British oil tanker on Wednesday and asked it to stop in Iranian waters close by, but withdrew after a British warship warned them over radio, a US defence official said on Thursday.