Tensions on the oil shipping lanes in the Gulf have escalated with the announcement of new naval exercises by Iran's Revolutionary Guards and news that Israel and the US are planning to carry out extensive joint manoeuvres in the region.

The naval commander for the Islamic Revolutionary Guards Corps (IRGC), Rear Admiral Ali Fadavi, said the drill in February would be "different compared to previous exercises held by the IRGC". The Iranian navy finished 10 days of exercises in the Gulf on Monday, during which it tested a range of new missiles. It warned that Iran could close the strait of Hormuz, the narrowest point in the Gulf, through which a fifth of the world's traded oil passes.

On the same day, the Israeli military said it was preparing for joint exercises with the US to rehearse missile defence and co-operation between the forces. The manoeuvres involve thousands of troops, have been planned for some time and were hailed by Israeli and US officials as their biggest joint drill.

Associated Press quoted an unnamed Israel official as saying the drill would test multiple Israeli and US air defence systems against incoming missiles and rockets in the next few weeks. Israel has developed the Arrow anti-ballistic system, which is designed to intercept Iranian missiles in the stratosphere, with the US.

The military activity in the region comes at a time of high tension. At the end of this month, EU foreign ministers are expected to agree to impose an embargo on Iranian oil imports, after a report in November by the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), confirmed western allegations that Iran had worked on nuclear weapon design.

Iranian officials have made clear they would view an oil embargo as an act of aggression, and could respond by closing the strait. The US and UK have said they would act to keep the shipping lanes open. Philip Hammond, the British defence secretary, said during a visit to Washington: "Disruption to the flow of oil through the strait of Hormuz would threaten regional and global economic growth. Any attempt by Iran to close the strait would be illegal and unsuccessful."

The sabre-rattling over the strait drove the price of crude to more than $100 a barrel. Meanwhile, there is continual speculation that Israel might attack Iran's nuclear programme, which Tehran says is for peaceful purposes, and which the west and Israel allege is a front for acquiring nuclear weapons, or at least a capacity to make them. Observers say all sides are flexing their muscles to deter their adversaries from taking aggressive action, but warn that heightened activity will increase the chances of an unplanned clash.

Mark Fitzpatrick, a former US state department official now at the International Institute for Strategic Studies in London, said: "I'm not predicting there is going to be a skirmish, but in the absence of established communications, the tensions and the activity raises the possibility of an unintended exchange of fire."

The USS John Stennis, a US aircraft carrier deployed to the region, is outside the Gulf and an Iranian navy commander has warned Washington not to bring it back. The US navy said it would continue to patrol the Gulf as normal.

Fitzpatrick said he did not think Iran would attack shipping through the strait of Hormuz "as it would be an invitation to the US to take wider action and attack its nuclear sites".

Another flashpoint could come in June, when US sanctions on the trade in Iranian oil come into effect. Gary Sick, an Iran expert and former White House policy adviser now at Columbia University, said such measures were "the equivalent of a military blockade of Iran's oil ports, arguably an act of war".

"The main reason why Iran's putative threat to close the strait of Hormuz was dismissed is because Iran also relies on the strait to export its own oil," Sick wrote in his blog. "But if Iran's oil revenue – 50% of its budget – is cut off, they would have little to lose by striking out at those they hold responsible, including passage through the strait of Hormuz.

"Iran cannot defeat the US navy, but the swarms of cruise missiles they could fire, both from shore and from their fleet of speedboats, could create havoc, as could the flood of mines they could put into the fast-moving waters of the strait."

Fitzpatrick said even under sanctions, Iran would still have "multiple markets for its oil", and would therefore still have a lot to lose by closing the strait.