EU foreign policy chief Kaja Kallas cautioned that U.S. involvement could escalate the Israel–Iran conflict.

"When it comes to the United States getting involved, then it will definitely drag the region into a broader conflict, and this is in nobody's interest," she told journalists in Brussels.

The trajectory of the confrontation between arch-rivals Israel and Iran may hinge on the next steps taken by U.S. President Donald Trump. Options range from pursuing a negotiated solution to direct military intervention, including providing "bunker-buster" bombs for attacks against underground nuclear sites.

In a phone call with U.S. Secretary of State Marco Rubio, Kallas said he had agreed with her that it was not in Washington's interest to be drawn into the fighting.

The EU's top diplomat held an emergency videoconference with the bloc's foreign ministers on Tuesday.

"It is clear that everybody agrees that Iran can't have a nuclear bomb, and that is our end goal," she said of the call, adding that a diplomatic outcome was generally considered the best long-term solution.

Another key issue discussed was the evacuation of EU citizens.

"We have member states that have planes evacuating. We have member states who don't have planes, and we coordinate the efforts so that our citizens are safe," Kallas said.