Oil prices have spiked back over a US$100 with some leading analysts now forecasting the possibility of prices reaching $US120.It comes after an escalation in conflict between the US and Iran over the few days with the US hitting a number of Iranian oil tankers in the Strait of Hormuz in response to an Iran attack on a US warship.The international benchmark Brent finished at up 3.4 percent today to US$101.21 a barrel after touching a high of US$101.58.While US West Texas Intermediate crude was up 3.25 percent, to US$96.05 a barrel.Both benchmarks closed at their highest since 22 May, according to Reuters news agency.Bloomberg News has reported that investment Bank Goldman Sachs has said oil prices may rally to as much ​as US$120 a barrel if attacks ‌on shipping in the Middle East rise.Oil prices had eased from early war highs in recent weeks after both Iran the US appeared to pull back on fighting.However, according to Reuters, shipping volumes through the Strait of Hormuz still remain far below their pre-war peak.The Strait is responsible for transiting about one-fifth of the world's oil and gas supply, making it key to the worldwide energy trade.The rise above US$100 a barrel was unwelcome news for Wall Street, which fell as markets nervously await US inflation data due this Friday evening.A higher CPI print, boosted by resurgent oil prices, could stoke fears that the Federal Reserve will have to hike interest rates this month, against a backdrop of rising bond yields globally.30-year US bond yields have already hit their highest level since 2007 this week.Meanwhile, prices for 91 unleaded petrol in New Zealand are sitting at just over $3 a litre.Westpac chief economist Kelly Eckhold expected that could rise given the recent increases in international markets.He said there was a danger now that the pro-longed nature of the conflict could mean some firms - who may have initially held off price increases from high oil prices - will no longer be able to do so.