Uncertainty surrounding peace negotiations between the U.S. and Iran has brought commercial traffic through the Strait of Hormuz to a virtual standstill, Bloomberg reported Tuesday.

Just two inbound commercial transits were observed Tuesday morning on the strait, a key shipping lane through which about 20% of global oil consumption passes. That followed two outbound vessels Monday, according to ship-tracking data compiled by Bloomberg.

President Donald Trump has expressed optimism that the U.S. can reach an interim peace deal with Iran soon. Tehran threatened to suspend talks because of Israel’s escalating attacks on Iranian-backed Hezbollah terrorists in Lebanon.

Iranian officials in Tehran are discussing their “final text” to send to the U.S., Iran’s semi-official Mehr news agency reported Tuesday, citing a person close to the negotiating team. Mehr said the country’s negotiators remain wary of the U.S., arguing Washington has breached previous pledges.

Shipowners had recently grown more optimistic that traffic would increase with guidance from the U.S., according to Bloomberg. Mehr reported Tuesday that 24 vessels transited the strait over the past 24 hours after obtaining permission from the Islamic Revolutionary Guard Corps.

The figure is difficult to confirm independently, according to Bloomberg, because electronic interference and tracking gaps suggest the total might bundle smaller coastal craft with large commercial ships.

Regional shipping remains disrupted by the U.S. blockade of Iranian vessels in the Gulf of Oman. The U.S. Navy has been preventing vessels from entering or leaving Iranian ports since the ceasefire began April 7. On Monday, U.S. military officials reported that a total of 121 commercial ships have been rerouted, Bloomberg reported.

Persistent Automatic Identification System, or AIS, interference continues to obscure vessel movements, with transit counts likely to be revised as ships reappear beyond high-risk waters, according to Bloomberg.

The U.S. naval presence might also be skewing observations. Iranian-linked vessels entering or leaving the Gulf could be switching off AIS signals to avoid detection, making it more difficult to track traffic flows in real time.

Even before the U.S. barred movement to and from Iranian ports, it was common for Iranian-linked vessels to “go dark” when approaching the Strait of Hormuz. Signals often were not restored until vessels reached the Strait of Malacca, about 13 days’ sailing from Kharg Island. The island is a strategic Iranian oil hub responsible for the vast majority of the country’s crude exports.