Oil is trading above $110 a barrel again, reaching five-month highs, as investors grow increasingly concerned about potential new Iranian action in the Strait of Hormuz — the critical maritime chokepoint through which roughly one-fifth of the world’s oil and natural gas supply passes.

On Thursday morning, North Sea Brent crude, the European benchmark, rose 0.7% to $110.32 per barrel, while West Texas Intermediate (WTI), the US benchmark, edged down 0.20% to $98.35 per barrel after approaching the $100 mark overnight. Amsterdam-traded natural gas fell 0.16% to €87.90 per megawatt-hour.

On Wednesday, Iranian Vice-President Reza Aref stated that the country has ‘no other choice’ but to secure control of the Strait of Hormuz to safeguard its national security, according to the state-run IRNA news agency. The remarks come as tankers continue to face attacks in the waterway and energy infrastructure across the Middle East remains in the crosshairs of Houthi rebels.

During a meeting with the Russian prime minister, Aref also said the Islamic Republic is guaranteeing passage through the strait for allied nations. However, he squarely blamed the United States for the current situation, declaring that ‘the US is responsible for the current situation and must pay the price for it.’ Despite the escalating tensions, Washington has asserted that crude oil flows through the Persian Gulf have recovered to 80% of pre-war levels.

‘The risks to oil prices are clearly tilted to the upside,’ said Hamad Hussain, commodities economist at Capital Economics, as quoted by Bloomberg. The analyst warned that the intensification of attacks on vessels raises the risk of a ‘fresh drop in oil supply and a continued rise in prices.’