BRUSSELS — French President Emmanuel Macron said Friday that NATO leaders must make a clear, unequivocal commitment to the military organization's values and rules at a summit next month — a thinly veiled swipe at Turkey's conduct within the alliance.

Macron ruffled feathers at NATO just ahead of the last summit in December 2019 when he lamented the "brain death" of the 30-nation alliance, due to a perceived lack of U.S. leadership under former President Donald Trump and unilateral military actions taken by Turkey in Syria without warning its partners.

Speaking to reporters in Paris Friday alongside NATO Secretary-General Jens Stoltenberg, Macron said the leaders, including U.S. President Joe Biden, must openly discuss "cohesion" within NATO at their June 14 summit in Brussels.

"That means to be clear among ourselves about the values, principles and the rules that underpin our Alliance," Macron said.

"Solidarity among allies is not simply a word that can mean anything at any time. It involves duties, responsibility to each other. It involves each ally committing to respect international law and clear rules of conduct," he said.

Macron said it's important for countries not to focus "on national interests that are contradictory to the security of other allies, as has been the case in recent years in Syria, the Eastern Mediterranean, Libya, in the Caucasus." He also mentioned the "interoperability of armaments, which is absolutely critical in NATO."

The French president did not mention Turkey by name, but Turkey has been widely criticized for its energy exploration work in contested parts of the Eastern Mediterranean. Last year, Turkish warships also prevented a French frigate policing the U.N. arms embargo on Libya from inspecting a cargo vessel.

Turkey's purchase of Russian-made S-400 missiles, which NATO says would compromise its own defenses, saw the country kicked out of the F-35 stealth fighter program by the United States. Despite this, it is understood in NATO circles that Ankara intends to buy more.

Stoltenberg said only that the leaders "will reinforce our unity and solidarity" in future.

"This means consulting more in NATO on all issues that affect our security, reaffirming our fundamental values, and strengthening our commitment to collective defense, including with increased investments," the former Norwegian prime minister said.