THE HAGUE, The Netherlands (AP) — President Emmanuel Macron said Monday that France doesn’t exclude sending fighter jets to Ukraine, but laid out multiple conditions before such a significant step might be taken.

France has sent Ukraine air-defense systems, rocket launcher units, cannons and other military equipment and has pledged to send armoured surveillance and combat vehicles, but has stopped short of sending battle tanks or heavier weaponry.

Asked at a news conference in The Hague on Monday if France is considering sending warplanes, Macron said “nothing is excluded” as long as certain conditions are met.

Among those conditions: that providing such equipment would not lead to an escalation of tensions or be used “to touch Russian soil,” and that it wouldn’t “weaken the capacities of the French army,” Macron said.

He also said Ukraine would have to formally request the planes. He noted that he will meet visiting Ukrainian Defense Minister Oleksii Reznikov in Paris on Tuesday.

Ukrainian officials have been stepping up demands for heavier weapons from Western allies to push back Russia’s forces.

At Macron’s side, Dutch Prime Minister Mark Rutte said Ukraine hasn’t formally requested Dutch F16 fighter jets so far. He struck a cautious stance after the Dutch foreign minister told lawmakers earlier this month that there were “no taboos” about sending the warplanes.

“There is no talk about delivering F-16s to Ukraine. No requests,” Rutte said Monday. There are “no taboos, but it would be a very big next step.”

“It is very important we keep supporting Ukraine and that Ukraine articulates to us what they need,” Rutte said.

He welcomed recent German and US announcements about sending tanks to Ukraine.

“As the Netherlands, we will keep looking at what we can do,” Rutte said. “We don’t have Leopard 2 tanks, we lease them. We’ve said if it helps we’re prepared to buy them and pass them on. Maybe it’s better to use those leased Leopard 2s somewhere else. … Whatever works.”