Oil prices were nearly flat on Thursday as investors weighed the impact of supply disruptions from the war in the Middle East after President Donald Trump warned that the U.S. military would hit Iran “very hard tonight.”

Hostilities between the U.S. and Iran have recently escalated. Trump said the U.S. will soon take control of Iran’s oil and gas infrastructure and markets while Washington launched additional strikes against the country. Meanwhile, Tehran declared the Strait of Hormuz closed.

Brent futures were down 12 cents, or 0.1%, to $92.98 a barrel by 1303 GMT, while U.S. West Texas Intermediate (WTI) crude gained 7 cents, or 0.1%, to $90.10.

Three Iranian sources and a European official said the U.S. and Iran were exchanging messages on details of a memorandum after reaching a political understanding, but some issues still had to be discussed in detail, including a mechanism for the release of billions of dollars in frozen Iranian funds.