The U.S. nearly turned into a net crude exporter last week for the first time since World War Two as shipments surged close to a record high to meet demand from Asian and European buyers scrambling to replace Middle East supplies cut by the Iran war.

The U.S. and Israel's war with Iran triggered the largest ever disruption to the global energy market as Iranian threats to shipping stopped around a fifth of the world's oil and gas supplies from transiting the Strait of Hormuz waterway.

Refiners in Asia and Europe that depend on those supplies have bought alternative cargoes from wherever they can, sharply boosting demand for oil from the U.S., the world's largest producer.

However, analysts and traders say the U.S. is rapidly approaching its export capacity.

Net imports of crude oil, or the difference between imports and exports, narrowed to 66,000 barrels per day last week, the lowest on record in weekly data that goes back to 2001, according to U.S. government data released on Wednesday, while exports climbed to 5.2 million bpd, the highest in seven months.

On an annual basis, the U.S. was last a net exporter of crude in 1943, data showed.

Rising U.S. crude exports are evidence that Atlantic Basin and Asian buyers are reaching further out for available supply, with regional oil price differences making up for the costs of shipping, said Rystad vice president of oil markets, Janiv Shah.

Countries such as Greece have snapped up U.S. crude for the first time ever in recent months.

About 2.4 million bpd, or some 47% of U.S. exports last week sailed toward Europe, according to ship tracking service Kpler. Around 1.49 million bpd, or about 37%, headed to Asia, up from 30% a year ago.

Top buyers included the Netherlands, Japan, France, Germany, and South Korea.

A vessel carrying 500,000 barrels of crude signaled it was en route to Turkey, which would mark the first U.S. export to the country in at least a year, Kpler data showed.

Imports to the U.S., meanwhile, dropped by more than 1 million bpd to 5.3 million bpd last week. The U.S. still imports a lot of its crude as its refineries are designed to take heavier, more sour grades than the light sweet crude it produces.

The disruption to Middle East supplies blew out the premium for Brent crude futures over U.S. West Texas Intermediate crude futures to as much as $20.69 a barrel last month, reducing U.S. buyers' appetite for imports, while making U.S. crude attractive to refiners in Europe and Asia.

The price of physical crude oil cargoes for prompt delivery to Europe hit a record high near $150 a barrel on Monday, and those for Africa hit new peaks, according to LSEG data and traders.

U.S. exports are likely to touch about 5.2 million bpd for April, Matt Smith, an analyst at Kpler said, adding that exports were pushing up against capacity limits on a monthly basis.

The U.S. can export as much as 6 million bpd, traders and analysts said, citing limited pipeline capacity and vessel availability. Its exports hit a record high of 5.6 million bpd in 2023, government data shows.

"The market is already testing the export ceiling with 5.2 million bpd exported last week. Every incremental barrel from here costs more in freight and logistics than the last one," according to Bekzod Zukhritdinov, a Dubai-based oil trader.

A release of medium sour crude from the Strategic Petroleum Reserve could push more light, low sulfur U.S. crude grades out for export, Rystad's Shah said. But a shortage of tankers, and higher freight rates could hurt that export demand, he added.

About 80 empty supertankers were heading to the Gulf of Mexico as of Wednesday, likely to pick up crude over April and May, said Rohit Rathod, a senior analyst at Vortexa.