So far this month the Iranian-backed Houthi rebels in Yemen have launched more than 20 drone and missile attacks against predominantly civilian targets in Saudi Arabia. Pictured: Supporters of the Houthis protest against the US designation of the Houthis as a terrorist organisation, on January 20, 2021, in Sanaa, Yemen. (Photo by Mohammed Huwais/AFP via Getty Images)
US President Joe Biden has good reason to regret his hasty decision to remove the terrorist designation applied to the Iranian-backed Houthi rebels in Yemen after they responded to his act of benevolence by unleashing a fresh wave of attacks in the Middle East.
The Houthis and their Iranian backers are primarily responsible for starting Yemen's long and bitter civil war after they overthrew the democratically-elected government of Yemeni President Abd-Rabbu Mansour Hadi in 2014.
Apart from helping to create what the UN has called the world's worst humanitarian disaster, the Houthis have also used the sophisticated weaponry they have received from Iran, such as drones and ballistic missiles, to broaden the conflict into neighbouring Saudi Arabia, which is leading the coalition military campaign to re-establish Yemen's democratically-elected government.
In one of their more outrageous acts of provocation, the Houthis fired missiles at Mecca, one of the holiest sites in Islam, and continually attack civilian targets in both Yemen and Saudi.
It was behaviour like this that prompted former US Secretary of State Mike Pompeo to designate the Houthis a terrorist organisation in the dying days of Donald Trump's administration.
Announcing the decision to designate the Houthi movement -- known formally as Ansar Allah (Partisans of God) -- as a Foreign Terrorist Organisation (FTO) on the day before Mr Trump left office, Mr Pompeo said the aim of the move was "to hold Ansar Allah accountable for its terrorist acts, including cross-border attacks threatening civilian populations, infrastructure, and commercial shipping."
The US action banned Americans from doing business with the Houthis and made it a crime to provide support or resources to the movement.
The move was promptly denounced by humanitarian and aid agencies, which claimed that designating the Houthis as terrorists would impede the global effort to help Yemen's starving population, an argument that appears perverse as the Houthis control most of the key aid supply routes, and regularly steal aid supplies to sell on the black market and fund their terrorist operations.
Responding to pressure from within his own Democratic party, Mr Biden, in one of his first acts as president, lifted the FTO against the Houthis, which was an act also seen as an attempt by the new administration to make a goodwill gesture to Iran.
Mr Biden has indicated he is keen to revive the controversial nuclear deal with Iran and, by easing the pressure on the Houthis, whose success on the battlefield is entirely due to the weapons and support they receive from Tehran, the White House was hoping to send a message to Iran that it was serious about having a constructive dialogue with Tehran.
Instead, in the weeks since Mr Biden lifted the FTO, the region has seen a significant increase in Houthi activity.
So far this month the Houthis have launched more than 20 drone and missile attacks against predominantly civilian targets in Saudi Arabia. In the most high profile attack, the Houthis used an explosive-laden drone and a ballistic missile against the Saudi petroleum plant at Ras Tanura, prompting global oil prices to rise above $70 a barrel earlier this week, its highest in more than a year.
The upsurge in violence by the Houthis and their Iranian backers is deeply embarrassing for Mr Biden, whose decision to lift the FTO designation against the Houthis last month now looks extremely ill-judged, to say the least.
"We continue to be alarmed by the frequency of Houthi attacks on Saudi Arabia," said White House press secretary Jen Psaki in the aftermath of the latest round of Houthi-inspired violence. "Escalating attacks like these are not the actions of a group that is serious about peace."
Mr Biden has now pledged to help strengthen Saudi air defences against further attacks by the Houthis and Iran, which is also embarrassing for the new administration, as only last month the Biden administration announced it was ending its support for the Saudi-led coalition in its war against the Houthis. Now it finds itself having to defend the Saudis against further Houthi acts of aggression.
The real lesson of this latest upsurge in Houthi-related violence, however, is that it shows that Mr Biden's hopes of reviving negotiations over Iran's nuclear programme are as flawed as his approach to the Houthis.
For, by helping to facilitate these attacks by providing the Houthis with sophisticated weapons, Tehran is showing that, far from seeking improved relations with the new US administration, it remains committed to pursuing an uncompromising policy of aggression throughout the Middle East, one that is unlikely to result in the resumption of talks on the problematic issue of Iran's nuclear programme anytime soon.
Con Coughlin is the Telegraph's Defence and Foreign Affairs Editor and a Distinguished Senior Fellow at Gatestone Institute.