Some of the world's largest oil traders have asked the US government to allow the tankers they have approved to return to service as a global shortage of ships is causing an extraordinary increase in the cost of transporting oil. The main problem is not the availability of crude oil, but the ability to transport it: tonnage blocked by sanctions is seen as a potential reserve in the context of an already existing shortage of tankers.
The immediate signal to the market is an increase in freight costs, which leads to an increase in the difference in the cost of supplying oil, especially in long-distance lines where the availability of ships is most important. If traders insist on returning the sanctioned vessels to circulation, this indicates that the shortage is so severe that it affects the economics of the trade, not just profits. Increasing available tonnage could reduce transportation constraints and reduce pressure on physical oil flows, but only if the US government grants the appropriate permits.
For the oil market, it is a reminder that logistical constraints can reduce effective supply even when oil reserves are officially available.