The country of Yemen, a critical U.S. ally in the "war on terror," could get a lot more unstable thanks to its government cutting a deal with Shiite Muslim rebels that resulted in the resignation of its leadership.

According to Nick Paton Walsh and Laura Smith-Spark of CNN, Yemeni President Abdu Rabu Mansour Hadi resigned from his post Thursday night shortly after the country's prime minister and cabinet stepped down. The shockwaves resulting from the resignations have reverberated around the world; Paul D. Shinkman of U.S. News & World Report thought that Yemen was "on the verge of collapse."

"The situation in Yemen changes hourly," Defense Secretary Chuck Hagel said Thursday during a press conference at the Pentagon.

Fox News reported that Hadi resigned after being pressured to make concession to the Shiite rebels, known as Houthis. That group managed to seize Yemen's capital, Sanaa, and confine the leader to his home for the past two days.

State Department spokesperson Jen Psaki commented on the developing events in Yemen and how the U.S. will assess that situation. Fox News reported that it remained unclear on who really controlled the country now.

"We are seeking a peaceful transition," she said.

According to CNN, the peace deal made by the Houthi rebels and the Yemeni government would hinder on officials rewriting parts of the country's constitution. If this was done, the rebels would withdraw their militias from key government institutions; CNN reported that they kidnapped Ahmed bin Mubarak, Yemen's presidential chief of staff, as collateral on Saturday.

"Under its terms, the government would accept changes in the draft of the new constitution that would grant the Houthis more political power," Walsh and Spark wrote.

CNN added that based on the tentative agreement, the Houthis wanted "marginalized political groups to have the right to partnerships in state institutions and fair representation."

Fox News reported that heavily armed Shiite rebels still remained outside Hadi's house and the presidential palace 24 hours after the deal was signed. However, the Houthis have previously negotiated with the Yememi government before, according to CNN.

"Houthis swept into the capital last year, sparking battles that left more than 300 people dead in a month," Walsh and Spark wrote. "In September, they signed a ceasefire deal with the government, and Houthis have since installed themselves in key positions in the government and financial institutions."

Shinkman argued that this event could threaten both regional and world security, given that some Islamic terror groups base their operations in Yemen.

"The country serves as home to al-Qaida in the Arabian Peninsula, considered the most potent offshoot of the al-Qaida extremist network and the one that most openly proclaims its desire to attack targets in the U.S. and elsewhere in the West," Shinkman wrote. "The Sunni Muslim group claimed credit for the Charlie Hebdo massacre in Paris earlier this month, though whether it was truly involved remains unclear."

In addition, the U.S. has conducted drone strikes within Yemen's borders. The new chairman of the House Armed Services Committee, Rep. Mac Thornberry (R-Texas), confirmed on Thursday that fewer information-surveillance-reconnaissance drones, or ISR, have been deployed to Yemen due to the ISIS threat in Iraq and Syria.

"Yemen is the place from which the most serious threats against our homeland have emanated," Thornberry said. "We still have a limited number of ISR available, so if you have to do more - we had nothing, especially in Iraq and Syria, so if you're going to do something there it has to come from somewhere."

Although U.S. News & World Report failed to get Thornberry to elaborate on how many U.S. drones and assets were in Yemen now, he did state that there is "a lot less activity there than there used to be."

However, the U.S. defense secretary is paying keen attention to the events in Yemen, which, according to Shinkman, "could go either way" at the moment.

"We were well aware of the danger and uncertainty and what was going on there before today," Hagel said Thursday.