Global oil prices are nearing a key trading threshold heading into a dearth of headline drivers for broader markets, and that could mean faster inflation pressures, higher Treasury bond yields, and renewed equity volatility over the coming weeks.

President Donald Trump raised the prospects of a longer, and potentially deeper, military campaign in the Gulf region last night when he responded to demands from Iran for compensation tied to a war that is nearing its six-month anniversary.

The strident approach from both sides, alongside a new series of threats and attacks on Saudi Arabia from Iran-backed Houthi rebels in the Red Sea, has triggered a renewed spike in global crude prices.

Brent crude futures for October delivery, the global pricing benchmark, touched $90 a barrel in overnight trading, extending its one-week gain to around 13%. The contracts were last marked at $87.91 a barrel.

WTI futures for September delivery, which are more tightly-linked to U.S. gasoline prices, have risen more than 10% over the past week and are more than 25% higher than when the conflict began in late February.

"Oil prices remain supported by uncertainty surrounding the Strait of Hormuz," said ING's head of commodity strategy Warren Patterson. "While Trump said Washington is 'semi-negotiating' with Iran, suggesting a focus on economic pressure rather than military escalation, significant hurdles remain before any broader agreement is reached."

U.S. crude stockpiles, meanwhile, are falling to dangerous levels as the war on Iran continues, and threatens to escalate.

Holdings in the Strategic Petroleum Reserve fell by 6.1 million barrels last week, according to Department of Energy figures, taking the overall tally to just under 300 million. That's the lowest level since 1983 and less than half of the SPR's 714 million barrel capacity.

That reduces the U.S.'s ability to respond to further supply shocks, an issue that remains of acute concern for markets as the Strait of Hormuz remains severely limited to oil and energy traffic and a deal to have it reopened remains elusive.

"We're now at a point where traffic hasn't been anywhere near pre-conflict levels for over 6 months," said Henry Allen, macro strategist at Deutsche Bank.

"Tariffs remain a feature of the global economic landscape. And we even have the prospect of a very strong El Niño occurring later this year, which would likely add to the upward pressure on food and energy prices," he added. "Given the array of inflation risks right now, and the volatility we've seen in energy markets of late, it's striking that investors are pricing in broadly contained inflation."

U.S. gasoline inventories, meanwhile, are sitting at their lowest levels in more than a decade, according to energy market analyst Lukas Ekwueme, a factor that is certain to stoke domestic costs over the coming months.

The average price per gallon still sits north of $4, according to AAA data, and remains more than 28% higher than levels seen at this time last year.

"With the Strait remaining closed, upward pressure on fuel prices could return quickly, and if things don't go well, the national average could climb to its highest level ever recorded this late in the calendar year, " said Patrick De Haan, head of petroleum analysis at the consumer advocacy group GasBuddy.

That would have clear and direct implications for U.S. inflation readings, which are expected to have eased modestly in July but still remain well above the Federal Reserve's 2% target, a threshold Kevin Warsh has vowed to address as the central bank's new chairman.

"High inflation has left a mistaken impression -- that's hard to shake -- that the Fed's implicit inflation target was somehow above 2%," Warsh told reporters following last month's rate decision. "Let me reiterate: there is no soft inflation target. There's only a target, and it's 2%."

Oil, and by extension gas prices, will complicate reaching that target if the conflict lingers into autumn, or escalates quickly as negotiations fail, said Stephen Coltman, head of macro at 21shares.

"Caught between having to escalate the conflict to open the Strait and walking away and leaving Iran empowered in the region, the Trump administration is choosing to maintain the uneasy status quo and hope that Iran will fold under the economic pressure of the blockade," he said.

"If oil supplies remain cut-off, however, rising gasoline prices will also exert growing political pressure on Trump approaching the midterms, " he added. "The risk of a major oil price shock remains very real as strategic petroleum reserves cannot be run down indefinitely."