The Iran war has virtually halted activity in the key waterway, through which a fifth of the world's crude supplies and a substantial amount of gas normally run -- sending oil prices soaring.

"It is in our interest to keep the Strait of Hormuz open, and that's why we are also discussing what we can do in this regard," Kallas told journalists heading into the Brussels talks.

An option on the table would be to change the mandate of the EU's naval mission in the Red Sea, Operation Aspides, Kallas said.

She suggested this would be the "fastest" way for the 27-member bloc to boost security in the Strait of Hormuz, where Iranian retaliatory attacks to a US-Israeli bombing campaign have largely halted maritime traffic.

"If we want to have security in this region, then it would be easiest to actually already use the operation that we have in the region," she said.

But it remained to be seen whether EU countries were willing to use it to that end, Kallas added.

"We will discuss with member states whether it's possible to really change the mandate of this mission," she said.

- Sceptical capitals -

Several capitals indicated they were cold to the idea.

"The current mandate of Operation Aspides is correct and does not require any changes," Spain's foreign minister Jose Manuel Albares said arriving at the talks.

He was echoed by Italy's Antonio Tajani who expressed scepticism about the feasibility of extending the mission's mandate, adding Italy preferred a diplomatic solution to the crisis.

Germany's Johann Wadephul said Berlin wanted to first hear from Israel and the United States "when they believe they will have achieved their military objectives in Iran" before moving on to plan a "security architecture" for the region.

Launched in 2024 to prevent attacks on trade vessels by Iran-backed Houthi rebel forces, Aspides currently has three warships -- one French, one Greek and one Italian.

French President Emmanuel Macron said last week that Paris and its allies were preparing a "defensive" mission to reopen the strait.

He has also pledged to increase France's contribution to Aspides, with two additional frigates "over the long term".

Kallas said a "coalition of the willing" could also be considered, without providing further details.

On Sunday, US President Donald Trump urged NATO allies to help open the Strait of Hormuz, warning the alliance faced a "very bad" future if they did not.

His comments met with a frosty reception.

German Chancellor Friedrich Merz's spokesman said the Iran war had "nothing to do with NATO", while Polish Foreign Minister Radoslaw Sikorski stressed there were procedures within the alliance to request support -- and they were yet to be activated.