Militiamen loyal to President Abed Rabbo Mansour Hadi ride on an army vehicle on a street in Aden, Yemen, March 20, 2015.
Militiamen loyal to President Abed Rabbo Mansour Hadi ride on an army vehicle on a street in Aden, Yemen, March 20, 2015.

The ongoing crisis in Yemen has drawn increased focus from other countries in the region and its allies overseas, as the search for a political solution continues and rival factions in the north and south press their fight for control.

U.S. Ambassador to Yemen Matthew Tueller said Monday he is "relatively optimistic" that a new power-sharing agreement can be reached between the internationally recognized government of President Abd-Rabbu Mansour Hadi and the Houthi rebels who control the capital, Sana'a. But he told the Reuters news agency that decisions need to be made quickly.

"Political dialogue won't work if Hadi is overrun and captured, and Aden falls, which could happen very quickly," Tueller said.

President Hadi fled to Aden to try to establish authority there last month after escaping house arrest by Houthi rebels in Sana'a.  Aden has since seen clashes between forces backing Hadi and both those loyal to former leader Ali Abdullah Saleh and Houthi rebels.

Militia and security sources said Monday that pro-Hadi troops had fought off dozens of Houthis who had been sent toward Aden.

Meanwhile, Saudi Arabia's Foreign Minister Saud al-Faisal told reporters in Riyadh that Arab countries would take "necessary measures" against the Houthis if a peaceful solution to the crisis cannot be found.  He also condemned what he said was Iranian "interference" in Yemen.

The Shi'ite Houthis are accused of being backed by majority Shi'ite Iran, which is itself a regional rival of mainly Sunni Saudi Arabia.

Hadi has requested neighboring Gulf Arab countries to use military intervention against the Houthis, according to Yemeni Foreign Minister Riad Yassin.  He said Monday that "time is not on our side."

"We have requested this for the sake of speed because the factor of time is not in anyone's favor, especially not in the favor of those behind constitutional legitimacy, it's not in our interests as simple Yemeni citizens who do not wish to see more bloodshed or a further deterioration of the situation," Yassin said. "Any emergency intervention done now will be less costly and lead to a good resolution."

He did not say what any military intervention would entail, but said the Houthis must be stopped.

The growing unrest in Yemen has prompted allies to withdraw their military and diplomatic staffs.  A person familiar with the matter told Reuters on Monday that Britain had evacuated the last of its special forces from the country in recent days.  The move followed the withdrawal of its embassy staff last month.

U.S. officials announced Saturday that all remaining U.S. personnel had been evacuated from Yemen, a day after two suicide bombings claimed by the Islamic State group killed 137 people in two mosques in Sana'a.

The U.S. State Department said in a statement that the temporary relocation was due to “the deteriorating security situation in Yemen.”

Yemen has sunk into violence and chaos since a popular uprising ousted Saleh, the longtime strongman, in 2012.

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