Reuters
At the same time, the US is desperate for a nuclear deal with Tehran, reportedly giving ground on Iran's demand that it be able to operate advanced uranium centrifuges in a heavily fortified, bomb-proof nuclear facility carved into the inside of a mountain even after a deal is signed.
At the same moment the US is wiling to retreat on major nuclear demands in the hopes of a diplomatic breakthrough with Iran, the US's own allies are launching a military coalition aimed at restraining Iranian power.
The US has been trying to triangulate, aiding Operation Decisive Storm with logistical and intelligence support while attempting to reassure Iranian negotiators, who are currently meeting with their US counterparts in Lausanne, Switzerland.
The Yemen conflict presents an even more immediate problem for the US. As the Los Angeles Times reported on March 25th, Iran-allied Houthi rebels obtained US intelligence files left behind after raiding an air base in Sana, the capital.
The files were then passed on to Yemeni "officials" sympathetic to the Houthis, who are in turn suspected of relaying them to Tehran, according to the Times.
"This is a disaster for US counterterrorism efforts across the Horn of Africa," Robert Caruso, a former US Navy intelligence officer, explained to Business Insider by email. "While it would be irresponsible to say what may have been compromised, this is a nightmare for our military and especially our counterterrorism forces in the region."
Basically, the Houthi advance through Yemen may have just delivered crucial information about US intelligence operations in the Middle East to a US-listed state sponsor of terrorism. And that may complicate the US's efforts in both Switzerland and the Arabian Peninsula.
REUTERS
The US may want to reassure Iran that it is willing to spare it the embarrassment and potential strategic cost of an even greater escalation against the Houthis, like an Egyptian and Saudi ground invasion. US negotiators also may be hamstrung by the Iranian possession of fresh US intelligence.
"News reports that Iranian military advisers now have classified information about US military and intelligence operations is extremely disconcerting and could be used to harm Americans if the nuclear deal fails," Caruso wrote. "I think we will find later on that Iran deliberately targeted the airbase and the US facilities there to gather and exploit intelligence that could be used as leverage or to target Americans later on."
The problem of balancing the nuclear negotiations against other aspects of the US relationship with Iran unique to Yemen. The US has troops in Iraq fighting ISIS and providing air cover to Iranian-allied militant groups. Meanwhile Hezbollah, and Iranian proxy, has a presence on every continent and Iran has plotted against targets inside the US as recently as 2011, when an Iranian effort to assassinate the Saudi ambassador to the US at an upscale Washington, DC restaurant was uncovered.
The US and Iran are strategically intertwined in Iraq, while Iran has the capability and perhaps even the intention of seriously undermining US interests around the world. Tehran realizes that it has plenty of potential leverage over its US negotiating counterparts.
That might explain why Tehran has demanded so many concessions in the nuclear negotiations - and gotten them.