The European Union's foreign policy chief, Federica Mogherini, told US Secretary of State Mike Pompeo that he should pursue a policy of "maximum restraint, avoiding any escalation on the military side," she later told reporters.
The next day, Russian Foreign Minister Sergei Lavrov told the US diplomat that he hopes that the US will not increase its military presence to push back on Iran, noting that "the region is overburdened with conflict as it is".
Traditional US allies such as Australia and Canada have remained quiet. Even Gulf Arab states that openly oppose Iran, such as Saudi Arabia and the United Arab Emirates, seem cautious this week. Israel's Benjamin Netanyahu may be the only world leader who has proactively praised the Trump Administration's tough stance on Iran.
"Israel and all the countries of the region and all the countries who seek peace in the world should stand together with the United States against Iranian aggression," Netanyahu said yesterday at a ceremony to mark the first anniversary of the opening of the US Embassy in Jerusalem.
This US isolation comes as the Trump Administration accused Iran of supporting "imminent attacks" on US personnel in the region. It provided little evidence to support its case, but the State Department ordered all "non-emergency US government employees" to leave Iraq.
Last week, the US dispatched warships and bombers to the Middle East to deter what it deemed Iranian threats. Only days later, two Saudi oil tankers and a Norwegian ship were damaged in apparent acts of sabotage in the Gulf.
Many traditional US allies are concerned about the threat of yet another conflict in the region. European nations think that "the Americans are sitting across the ocean, whereas we're right on the doorstep of the Middle East," said Ellie Geranmayeh, a fellow at the European Council on Foreign Relations.
The US is the world's preeminent military power; it has been willing to swim against the tide of public opinion on foreign policy before. The 2003 US-led invasion of Iraq took place without the backing of the United Nations and was later dubbed illegal by Secretary-General Kofi Annan. When French Foreign Minister Dominique de Villepin gave a speech to the United Nations Security Council that expressed France's opposition to the conflict, he was applauded.
But even by the standards of the Iraq War, the US appears to be on its own on Iran this week. In the former conflict, Britain ultimately sent 45,000 troops to aid the US in the invasion of Iraq, and Australia and Poland sent smaller numbers, while other countries provided political support.
"This time around, the Americans are going to really struggle to even get the British on board," Geranmayeh said of the possibility of a conflict with Iran.
The US has said that it is not seeking war with Iran, but it has not ruled it out.
"We fundamentally do not seek war with Iran," Pompeo said during a visit to Sochi, Russia, this week. "We have also made clear to the Iranians that if American interests are attacked, we will most certainly respond in the appropriate fashion."
Some analysts think that reports that the US is considering options to dramatically increase the number of troops it has in the Middle East are part of a pressure campaign against Iran. But even that strikes many allies as a risky proposition.
"We are very worried about the risk of a conflict happening by accident with an escalation that is unintended," British Foreign Secretary Jeremy Hunt told reporters in Brussels.
The US has spent almost two years trying to convince Europe to join a "maximum pressure" campaign against Iran, but European nations have generally distanced themselves from Trump's Iran policy.
Many have spoken in favour of the 2015 nuclear agreement with Iran, reached between the US, Britain, France, China, Russia and Germany during the Obama Administration, even after Trump pulled the US out of the deal last year and imposed sanctions on Iran.
However, while the European Union has issued statements critical of Iran, they have not supported US claims of imminent Iranian attacks. Though Germany and the Netherlands said that they had suspended participation in a training mission for Iraqi troops, they cited general tension between the US and Iran.
A handful of countries take a harsher rhetorical line on Iran: among them are Israel, Saudi Arabia, the United Arab Emirates and Brunei. But other than Netanyahu, these parties have kept quiet this week. The United Arab Emirates said on Monday that four commercial ships off its eastern coast "were subjected to sabotage operations," but it has not named who it thought was behind the incident.
Saudi Arabia has focused on an attack using armed drones that targeted oil-pumping stations in the country. A statement from the official Saudi news agency said that it was important to face "terrorist entities, including the Houthi militias in Yemen that are backed by Iran".
Theodore Karasik, a senior adviser with Washington-based Gulf State Analytics, said it was not unusual for the UAE and Saudi Arabia to keep quiet about policies they support.
"Abu Dhabi wants these actions," Karasik said of the tension with Iran, "and Saudi [Arabia] tags along."
