The annual Halifax International Security Forum brings together senior Canadian, European and US military and civilian officials, and you can guess what was on everyone’s mind this year: What kind of foreign policy can we expect from President-elect Trump?

To be more specific, the crowd was eager to pump US participants, including a bipartisan delegation of US senators, about whether Trump would turn his back on NATO and cozy up to Russian President Vladimir Putin. Many asked whether the president-elect might hold an early meeting with Putin even before getting together with NATO allies -- which would send a dangerous signal.

The Europeans fear that Trump could sell out Ukraine in exchange for a deal with Russia on Syria. Any such deal, they say, would undercut the broader security and stability of Europe and the United States.

However, as several senators made clear at Halifax -- Trump would face bipartisan opposition within the US Senate if he recognized Russia’s annexation of Crimea and its invasion of eastern Ukraine.

What was striking in Halifax was Europeans’ uncertainty about Trump’s intentions due to his public disdain for NATO and his constant praise for Putin. At a time when Putin is trying to facilitate the rise of the radical right in Europe as well as the breakup of the European Union, Trump appears ready to help him. (Cheering on Britain’s exit from Europe is a prime example.)

So the Europeans were anxious to know whether Trump really meant what he said about NATO or even grasped the impact of his words.

“The erosion of confidence and trust is corrosive,” said Pauline Neville-Jones, a former British government security minister, at a panel on NATO. “We need more NATO not less NATO,” added Croatian President Kolinda Grabar-Kitarovic. “The situation in the world requires cooperation between Europe and the United States.”

The test case for Trump’s intentions will be whether he plays Putin’s game on Ukraine.

During the campaign, candidate Trump indicated he might recognize the Russian leader’s annexation of Crimea (and ignore Moscow’s destabilization of eastern Ukraine). The Russian invasion of Ukrainian territory in 2014 ended the post-World War II understanding on the continent that sovereign boundaries would not be changed by force. It also violated the 2004 Budapest Memorandum under which Moscow and Washington guaranteed the territorial integrity of Ukraine in return for that country giving up its nuclear weapons.

Yet Trump operatives gutted the Republican Party platform’s support for Ukraine. Rumors have swirled that the president-elect might be open to lifting sanctions on Russia imposed over Putin’s invasion of Ukraine in exchange for some kind of deal on fighting the Islamic State group in Syria.

Never mind that Russia has shown little interest in fighting the Islamic State group, preferring to leave that dirty work to the Americans or the locals. Never mind that Moscow is mainly interested in cementing the control of its Syrian proxy, President Bashar al-Assad, and getting American buy in. Never mind that a deal with Moscow is effectively a deal with Tehran, which wants Assad in power because he lets them transfer arms via Syria to Hezbollah in Lebanon -- in order to fight Israel.

But let us return to the cost of recognizing Putin’s invasion of Ukraine.

“If you give up now on recognition of the annexation of Crimea, one of the building blocks of post-WWII peace will have been ruined,” I was told by Ukraine’s vice prime minister, Ivanna Klympush-Tsintsadze, at the Halifax Forum. If Trump breaks the unified Western stance against the Russian invasion, she added, Putin will use that fracture to widen other divisions in the alliance.

Moreover, a sellout of Ukraine would raise further questions about America’s commitment to the NATO alliance. After betraying the commitments to Ukraine made in the Budapest Memorandum, how would Washington get other nations to trust it on NATO guarantees, asks the Ukrainian leader? If Russia sends “little green men” (the euphemism for Russian soldiers without military insignia) into NATO member countries such as Latvia or Estonia, would Trump even care?

Of course, many presidents have believed that they could change Russia’s direction. George W. Bush tried it; at President Obama’s behest, Hillary Clinton initiated a “reset” with Moscow (which candidate Trump derided). Now Trump thinks he alone can pull it off.

However, “Putin is not ready for compromise,” the Ukrainian minister warns. “He is thinking in zero-sum terms, but he backs off if the West holds the line.” Putin would have invaded farther into Ukraine had not the West finally taken a stand, she adds.

If Trump isn’t willing to listen to European leaders on Ukraine, he might be persuaded by Congress, where Republican Party stalwarts such as Sen. John McCain have taken a firm stand on the issue, as have many other senators.

At the forum, Sen. Chris Coons of Delaware told me, “If President-elect Trump moved swiftly to try and trade Ukraine and Crimea and Syria with Putin, there would be strong bipartisan pushback. Many of the members have visited Ukraine and recognize the cost and consequences of Russian aggression.

“For Trump to try and turn on a dime and change our national approach to Putin, who has undermined democracy across Europe, would have drastic consequences for his standing in Congress and with the American people.”

That does not mean that the president-elect cannot have dialogue with the Russian leader. But he faces a steep learning curve on how to deal with Putin and avoid disaster over Ukraine. There will be serious security consequences for America and Europe if Trump simply plunges ahead.

By Trudy Rubin

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer. -- Ed.

(Tribune Content Agency/The Philadelphia Inquirer)