America is not seeking a war with Iran, but will also not rule out retaliation after a drone strike left three US soldiers dead in Jordan over the weekend.
US National Security Council spokesman John Kirby made the comments on Monday evening, saying Joe Biden's administration wants a "stable, secure, prosperous Middle East".
It comes as US President Joe Biden faces growing pressure to respond, with some Republicans - including Donald Trump - accusing him of being "ineffective, and weak".
Sunday's strike on an American military base - known as Tower 22 - in northeastern Jordan, has been blamed by the US on an Iran-backed group.
Iran's foreign ministry has denied any involvement in the strike, which also injured 34 people.
On Monday night, the Defense Department released the names of the three soldiers killed in the attack: Sgt. William Rivers, 46 of Carrollton, Georgia, Specialist Kennedy Sanders, 24 of Waycross, Georgia, and Specialist Breonna Moffett, 23, of Savannah, Georgia.
The parents of the youngest victim, Sanders, said Monday she had volunteered to deploy, eager for a chance to see a different part of the world.
“She was loved. She didn’t have any enemies. All the time you saw her smiling,” her father, Shawn Sanders, said in an interview. “This is somebody who was just living life, enjoying life at a young age, working toward a career.”
They were all assigned to the 718th Engineer Company, a Pentagon spokesperson said.
In a joint press conference with Nato Secretary General Jens Stoltenberg on Monday evening, US Secretary of State said America will "respond decisively to any aggression and we will hold responsible the people who attacked our troops.
"We will do so at a time and place of our choosing," he added.
In a warning to "anyone looking to take advantage of conflict in the Middle East", Blinken said: "Don't do it".
Speaking on what the US response could be, Blinken said: " it could well be multi-levelled, it could come in stages, and it could well be sustained over time".
The attack that forces Biden to make a decision that may change the Middle East
The three deaths are the first US fatalities to emerge from months of strikes by Iranian proxy groups against American forces across the Middle East.
There have been more than 150 militia attacks on US forces in the region since proscribed terror group Hamas launched its surprise attack into southern Israel on October 7.
Mr Biden has pledged the United States "will hold all those responsible to account at a time and in a manner [of] our choosing".
Two US officials have claimed the drone which caused the strike could have been confused with an American drone returning to Tower 22.
The officials told The Wall Street Journal, under the condition of anonymity, that a preliminary report had suggested as the enemy drone was flying in at a low altitude, a US drone was returning to the base and may have been let pass by mistake.
UK Prime Minister Rishi Sunak has urged Iran to "de-escalate tensions", whilst reiterating British support for the US.
He told broadcasters: "We absolutely condemn what has happened over the past couple of days.
"My thoughts are with all of those impacted, those who lost their lives, their families and those that are injured."
Sir Keir Starmer said those behind the drone strike should be "held to account", but expressed fears about the febrile situation widening.
"I am concerned about the possibility of escalation of an already dangerous situation in the Middle East," the Labour leader said
"So we have to see this in that context and do everything that we can to ensure there isn't escalation of the conflict, and on the contrary, that we find ways to bring this conflict to the immediate end."
Iranian-backed militias have said that their strikes are in retaliation for Washington's support for Israel in its war against Hamas.
America in recent months has hit targets in Iraq, Syria and Yemen in response to attacks on its forces, and to diminish the threats from Iranian-backed Houthi rebels to commercial shipping in the Red Sea.
US troops have long used Jordan, a kingdom bordering Iraq, Israel, the Palestinian territory of the occupied West Bank, Saudi Arabia and Syria, as a basing point. Some 3,000 American troops typically are stationed across Jordan.
Tower 22 sits near the demilitarised zone on the border between Jordan and Syria, and is only six miles away from the Iraqi border.
