BERLIN (AP) — Defense Secretary Ash Carter said the U.S. and NATO need to have a “strong but balanced” approach to Russia, and he questioned whether Moscow’s “backward-looking” aggressive behavior will change while President Vladimir Putin remains at the helm.

Speaking to reporters traveling with him to Europe Sunday, Carter said he can’t be certain Putin will change direction, so allies must use a two-pronged approach that works with Russia on some issues while also girding to deter and respond to Moscow’s aggression.

“The United States at least continues to hold out the prospect that Russia, maybe not under Vladimir Putin, but maybe sometime in the future, will return to a forward-moving course, rather than a backward-looking course,” said Carter, just before arriving in Berlin.

The Pentagon chief, who will attend his first NATO meeting as secretary this week, said he wants to lay out America’s balanced approach, which involves bolstering Europe’s military ability to deter Russia’s military actions. At the same time, allies need Moscow as they fight terrorism and hammer out a nuclear agreement with Iran.

Carter’s trip comes as the European Union is expected to extend economic sanctions against Russia until January to keep pressure on Moscow over the conflict in eastern Ukraine. And it follows Putin’s announcement that he will add more than 40 new intercontinental ballistic missiles that are capable of piercing any missile defenses. 

Putin’s remarks about the missiles were deemed “nuclear saber-rattling” by NATO Secretary-General Jens Stoltenberg. Carter called it inappropriate behavior.

Carter is expected to give a speech in Berlin, travel to Estonia, and attend a NATO defense ministers’ meeting this week.

A key theme at all his stops will be how the United States, NATO and other partners can best deal with the Kremlin in the wake of Moscow’s annexation of Ukraine’s Crimea region and its military backing of separatists battling Ukraine’s government on the eastern border. 

But part of the calculous, Carter said, will be a new playbook for NATO that deals with Russia’s aggression while also recognizing its important role in the nuclear talks with Iran, the fight against Islamic State militants and a peaceful political transition in Syria.

Officials said Carter, who left Washington on Sunday, plans to encourage allied ministers to better work together in countering threats facing Europe. His talks are sure to draw Putin’s ire as Moscow chafes under the prospect of continued sanctions.

Carter also intends to talk with counterparts about a U.S. proposal to send to Eastern Europe enough tanks, Humvees and other military equipment to outfit one brigade. 

The equipment would be used for exercises and other training programs, but more importantly would allow a faster NATO response to a crisis in the region. The idea of placing it in Eastern Europe as part of military measures to reassure allies has been in discussion for months; Carter has yet to give his final approval. 

Generally, a brigade has roughly 3,500 troops. 

Officials have not said where the equipment would go, but there are indications that Poland, which borders Russia, might be one location. 

Poland Defense Minister Tomasz Siemoniak said last week that he has been in talks with Carter about putting the equipment in Poland and in four other eastern NATO nations.

Just two weeks ago Carter convened a meeting of American defense and diplomatic leaders from across Europe, and concluded that the U.S. needs to strengthen its military exercises and training with nations in the region and bolster NATO’s intelligence-sharing to better counter Russia. 

He also acknowledged that the current international economic penalties against Russia have not stopped Moscow’s military support for separatists in Ukraine. He said that the U.S. and allies worry that Russia may use similar tactics and aggression against other nations in the region. 

Western leaders say Moscow is supplying rebels with manpower and powerful weapons, and have detailed Russian troop movements along Ukraine’s eastern border, including convoys of supplies, troops and weapons moving to bolster the separatists. Russia rejects those claims as unfounded. 

A fragile cease fire in Ukraine that was worked out in February has been broken repeatedly, and both sides blame the other for the spikes in violence.

At an investment conference Friday in Russia, Putin blamed the U.S. and the European Union for triggering the Ukrainian crisis by refusing to take into account what he described as Russia’s legitimate interests.

“They have pushed us back to the line beyond which we can’t retreat,” he said. “Russia isn’t seeking hegemony or some ephemeral superpower status.”

While Russia may dominate much of the talks, the allies also will discuss how NATO can provide more assistance to Iraq, including plans to involve the alliance more officially in the fight against Islamic State militants.

According to U.S. officials, NATO leaders will consider providing ministry-level advice and other training assistance in Iraq, with a possible decision approving the plan expected around July. 

Some allies are participating individually in the fight against IS, but NATO has not agreed on how it should weigh in as an alliance.