"We are going into crisis mode", a source at Whitehall told the Sky News broadcaster.
The current level of crisis is still low, but it could go up if the situation becomes aggravated, the media added.
Another source told the media that the number of additional Foreign Office workers focused on Iran had increased fivefold.
The news comes after the United States reinforced its military presence in the Persian Gulf with the Abraham Lincoln aircraft carrier and a bomber task force to send "a clear and unmistakable message" to Tehran. Washington approved the additional deployment of the Patriot missile defence system and Arlington amphibious warship to the region last weekend. Iran has, for its part, repeatedly expressed its readiness to retaliate in the event of a military conflict.
Last week, Tehran announced it was suspending some of its obligations under the Joint Comprehensive Plan of Action, which was signed in 2015 to limit the country's nuclear activity.
The decision came a year after the United States pulled out of the deal and reinstated wide-ranging sanctions on Tehran, including restrictions against companies and financial institutions of countries that do business with the Islamic republic. Iranian President Hassan Rouhani has given European countries 60 days to organise talks on the matter.
