China is seeking guarantees from Iran that its oil and liquefied natural gas tankers can safely pass through the Strait of Hormuz amid rising regional tensions.

The conflict has effectively blocked one of the world’s most important shipping routes, disrupting roughly one-fifth of global oil and gas supplies. China, a longtime ally of Iran, transports about 45% of its crude oil through the strait, The Caspian Post reports via foreign media.

Earlier this week, Iran stated that it would deny passage to vessels from the U.S., Israel, European countries, and their allies, though China was not mentioned in the announcement.

The regional tensions have already caused oil prices to surge more than 15% due to halted production and Iranian attacks on energy infrastructure in the Persian Gulf. Tracking data from Vortexa and Kpler show around 300 oil tankers currently in the strait, highlighting the growing risk to global energy markets.