Here’s a regional riddle: What do Lebanon, Syria, Yemen, and Iraq have in common? Hint: They’re all home to local militant groups, many of whom are on the U.S. designated terrorist list. Are you still unsure? The answer comes with a single word -- Iran. All of these countries have sizable armed groups that receive financial backing from the Shia-majority state.

Following a long-awaited nuclear deal between Iran and the P5+1 countries on Tuesday morning, critics fear the deal will bolster the enemies of U.S. allies., providing a catalyst for further conflict in the region.

Iran’s network of proxies -- the Houthis in Yemen, Hezbollah in Lebanon and regime-supporting groups in Syria -- has helped it to become a Shiite powerhouse, frequently jousting with Saudi Arabia, its dominant Sunni counterpart, for top position in the Middle East.

“There’s no doubt that it’s going to strengthen those Iranian proxy forces throughout the region,” said Russell A. Berman, a senior fellow at the Hoover Institution, a public-policy think tank based at Stanford University in California. “Initially it will be a source of moral encouragement. Secondly, it will mean they will be using their resources now in anticipation of greater resources.”

The White House hopes funds for the deal will be used to improve the lives of civilians following the lifting of international sanctions but Israeli Prime Minister Benjamin Netanyahu has described the terms of the deal as providing Iran with a “cash bonanza.”

If Iran does spread its wealth to its proxies sectarian fighting between rival groups could increase. Suzanne DiMaggio, a senior fellow and the director of the Iran Initiative at New America, a nonprofit American policy think tank says sectarian divides are already increasing. “This is an area where the U.S. could play a moderating role in trying to restore some balance in the region,” she says.

In the past year, Houthi rebels in Yemen toppled the former U.S.-backed government and are now fighting Saudi forces. In Lebanon, Hezbollah’s increasing power has its sworn enemy Israel on edge. Hezbollah and Iraqi Shiite militias are embroiled in civil and sectarian conflicts in Iraq and Syria, where they’ve emerged as a formidable fighting force.

"President Assad sends sent congratulatory messages to the leader of the revolution in Iran and the Iranian President on the occasion of the final agreement between Iran and the 5 + 1."

In a television announcement in April, Hezbollah leader Hassan Nasrallah responded with considerable enthusiasm to the preliminary Iran deal. “A rich and strong Iran… will be able to stand by its allies and friends, and the peoples of the region...more than in any time in the past.” Sources close to Hezbollah told International Business Times that additional Iranian support would not come in the form of weaponry, but rather in the form of institutional resources -- schools, hospitals and roads -- increasing local support, while propping up Shiite militias and regime forces in neighboring Syria.

Iran continues to fund Syrian President Bashar Assad’s army, the regime’s Syrian National Defense Forces and Afghan militias. Tehran also recently approved a $1 billion credit line to Syria, according to the Institute for the Study of War (ISW.)

“In terms of actual metrics, we would expect to see further direct financial support to the Assad regime, as well as support through direct oil exports,” said Christopher Kozak, a Syria Analyst at ISW. “This trend will likely accelerate as Iran acquires more financial capital.”