The White House on Tuesday warned that there was "no military solution" to the political upheaval in Bahrain, after a Saudi-led force intervened in a move which sent Gulf tensions rocketing.
The Saudi-led Gulf Cooperation Council force marched into the key strategic state of Bahrain, which hosts the headquarters of the US Fifth Fleet, to bolster the long-ruling Sunni monarchy against rising Shiite protests.
"We call for calm and restraint on all sides. We are particularly concerned by the increasing reports of provocative acts and sectarian violence by all groups," said National Security Council spokesman Tommy Vietor.
"The use of force and violence from any source will only worsen the situation," Vietor said in a statement that did not mention key US ally Saudi Arabia but which seemed clearly aimed at Riyadh.
"One thing is clear: there is no military solution to the problems in Bahrain.
"A political solution is necessary and all sides must now work to produce a dialogue that addresses the needs of all of Bahrain's citizens."
Vietor urged all parties in Bahrain to act responsibly and said that Jeffrey Feltman, a senior State Department official, was working "aggressively" in Bahrain to try to bring about a political solution.
Bahrain's king earlier declared a three-month state of emergency as two people died in fresh violence and Iran condemned the intervention by the Gulf Cooperation Council force.
Saudi Arabia's staunchly Sunni government said it had responded to a call for help from its neighbor under a mutual defense pact of the six-country GCC.
But Iran said the military intervention in a Shiite-majority country it has historic claims to was unacceptable.