By Phil Stewart
WASHINGTON (Reuters) - The United States is seeing growing indications that Iran-allied Houthi rebels, despite denials, were responsible for Sunday's attack on a Navy destroyer off the Yemen coast, U.S. officials told Reuters.
The rebels appeared to use small skiffs as spotters to help direct a missile attack on the warship, said U.S. officials, who are not authorized to speak publicly because the investigation is ongoing.
The United States is also investigating the possibility that a radar station under Houthi control in Yemen might have also "painted" the USS Mason, something that would have helped the Iran-aligned fighters pass along coordinates for a strike, said the officials.
Neither of the two missiles fired from Houthi-controlled territory on Sunday hit the USS Mason or the nearby USS Ponce, an amphibious transport dock. But the incident threatens to trigger the first direct U.S. military action against Houthis in Yemen's conflict, even if it is limited to one-off retaliation.
The Houthis have publicly denied any role in the strike. A senior Western diplomat told Reuters those denials have been communicated privately as well.
But the emerging details of Sunday's incident, if confirmed by a U.S. investigation, would lend further support to the Pentagon's claims that "the facts certainly seem to point" to Houthi involvement. The U.S. military even hinted on Tuesday at possible preparations for a retaliatory strike.
"Anybody who takes action, fires against U.S. Navy ships operating in international waters, does so at their own peril," Pentagon spokesman Captain Jeff Davis told a news briefing.
The Houthis, who drove the Saudi Arabia-backed Yemen President Abd Rabbu Mansour al-Hadi from the capital in 2014, had previously avoided targeting U.S. military ships.
Although the United States has provided limited support for the Saudi-led coalition battling the Houthis, it also has reserved its direct military role in Yemen to the fight against al Qaeda's affiliate, al Qaeda in the Arabian Peninsula.
That general U.S. policy might still remain in place, even if it opts to carry out one-off retaliatory strikes.
Yemen's war has killed at least 10,000 people and brought parts of the country to the brink of starvation.
The Houthis, who are allied to Hadi's predecessor Ali Abdullah Saleh, have the support of many army units and control most of the north including the capital Sanaa.
The U.S. military has acknowledged that only the first of the two missiles came close enough to even trigger the USS Mason's defenses, and it is still not clear those were necessary to avoid a direct hit on the ship.
It is also not clear whether those defenses caused the missile to splash down early, or whether it would have fallen short anyway.
The second missile, fired about an hour later, was far enough away that the USS Mason did not deem it necessary to employ its defenses.
But Reuters has learned that the coastal defense cruise missiles themselves had considerable range, adding to concerns about the kind of heavy weaponry that the Houthis appear willing to employ and some of which U.S. officials believe is supplied by Iran.
The second missile, for example, traveled more than two dozen nautical miles before splashing into the Red Sea off Yemen's southern coast, one of the officials said, speaking on condition of anonymity.
The Houthis had previously acknowledged responsibility for firing on a vessel from the United Arab Emirates a week earlier. Both incidents took place around the Bab al-Mandab strait, one of the world's busiest shipping routes.
Gerry Northwood, chief operations officer with British maritime security firm MAST, suggested the Houthis would find it increasingly difficult to stage similar strikes going forward.
"Now that the U.S. is getting involved, it will become increasingly difficult for the Houthis to position their missiles for further attacks," Northwood said.
(Reporting by Phil Stewart; Additional reporting by Jonathan Saul and Idrees Ali; Editing by Lisa Shumaker)