WASHINGTON: Global crude oil prices rose to three-week highs for a fourth consecutive day Wednesday as uncertainty over a ceasefire between the United States and Iran and disruptions to oil shipments through the Strait of Hormuz continued to weigh on markets.

According to Reuters, Brent crude futures for October delivery rose 45 cents, or 0.49%, to $91.47 a barrel. U.S. West Texas Intermediate crude also gained 45 cents, or 0.53%, to $85.39 a barrel.

Later in the session, Brent climbed further to $91.56 a barrel, while WTI rose to about $85.53.

Investors remained focused on when commercial shipping through the Strait of Hormuz would return to normal. Reuters reported that shipping activity through the strategic waterway remained well below normal levels, with several shipowners avoiding the route because of security risks.

The disruption has also created difficulties for Russia, while rising gasoline prices are adding to political pressure on President Donald Trump ahead of the U.S. midterm elections.

Trump has repeatedly accused oil companies of making excessive profits amid rising gasoline prices and has threatened to impose additional taxes on them. Oil companies have rejected the allegations.

The Strait of Hormuz is one of the world’s most important oil transit routes, carrying more than 20% of global oil and gas supplies. Iran has closed the waterway in response to U.S. and Israeli attacks, further increasing uncertainty in global energy markets.