Trump has left the door open for further strikes against the Islamic republic: File Image/Pixabay.

Weekend attacks on Saudi Arabia by Iran-backed Houthis took second stage in analytical and oil trading interests to the prospect of additional diesel supplies from Russia – the outcome being that two key benchmarks on Monday declined, albeit minimally.

Brent dipped by 61 cents to $106.04 per barrel by 0000 GMT while West Texas Intermediate declined 47 cents to $93.27 per barrel.

While the cause of optimism was U.S. president Donald Trump stating that Russia had agreed to immediately supply more than 300,000 tons of diesel to global markets, and Washington temporarily lifted U.S. sanctions on Russian fuel, lawmakers warned that Trump's agreement with the former Soviet Union may violate U.S. law barring imports of Russian energy until Moscow ends its aggression against Ukraine.

If the agreement holds, Russia will supply another 500,000 tons next month, 1 million tons “immediately thereafter” and 3 million tons “within a short period of time” depending on the condition of its diesel refineries, according to Trump.

For his part, Patrick De Haan, analyst at GasBuddy, said on Monday he was “skeptical” the deal would “deliver significant relief to the trucking industry and consumers who depend on diesel.”

Casting a familiar pall over Monday’s trading were ongoing U.S./Iran hostilities, and Tim Waterer, chief analyst at KCM Trade, remarked, "Fresh diesel supply from Russia and steadier Saudi flows are offering some relief, yet the market still looks more worried about the risk of further hits to ships or pipelines in the Gulf than it is reassured by extra barrels.

"Until we see clearer signs of de-escalation, the path of least resistance still leans higher."

But in all likelihood, hostilities are projected to increase, not decrease. Following the Houthi attack on two Saudi airports over the weekend that killed 13 people, Trump said the U.S. may “join” Saudi Arabia in delivering a response: “We will make a decision; we move very quickly,” he told reporters.

Also, when asked whether Washington would take action against Iran after Britain and its allies linked Tehran to the recent terror plot at RAF Fairford, Trump left the door open to more Iran strikes by replying “We’re going to see….. As soon as the war with Iran ends, which will be very soon with Iran, the oil will drop like a rock, and it's going to end very soon.”

In other oil news on Monday, Evgeni Simeonov, Lukoil's special commercial manager in Bulgaria, told media that insurance costs for ships transporting oil across the Black Sea have surged from approximately $200,000 to $2.5 million per vessel in recent months, a 12.5-fold increase.

London's marine insurance market had already expanded its Black Sea high-risk reporting requirements in September to cover the entire basin.