BRUSSELS: The United States is not yet ready to cooperate militarily with Russia, Pentagon chief James Mattis said on Thursday after Moscow’s defence minister called for better ties.

“We are not in a position right now to collaborate on a military level, but our political leaders will engage and try to find common ground or a way forward,” Mattis told reporters at a Nato summit in Brussels.

Russian Defence Minister Sergei Shoigu said earlier in Moscow that he was potentially “ready to restore cooperation with the Pentagon,” and President Vladimir Putin called for Russian intelligence agencies to bolster contacts with US counterparts in the counter-terrorism fight.

The back-and-forth remarks come as President Donald Trump faces a crisis over ties between Russia and members of his campaign team.

The new president has repeatedly praised Putin and called for better cooperation with Russia, including in the fight against the militant Islamic State group in Syria.

But Mattis, a former Marine general, said Russia must first “prove itself” and follow international law before the US and Nato can consider closer military ties.

“The point about Russia is they have to live by international law just like we expect all nations on this planet to do,” Mattis said.

Currently, the US-led coalition fighting IS in Syria and the Russian military, which is operating nearby in support of President Bashar al-Assad, do not cooperate but hold regular phone calls to avoid mid-air mishaps.

Mattis added he had “very little doubt” Moscow interfered in several elections, though he did not specifically mention the United States.

US intelligence agencies say the Russian government was involved in hacking Democratic Party communications and releasing files embarrassing to Trump’s rival Hillary Clinton.

The new Pentagon chief’s Nato visit, his first trip to Europe, was closely watched by jittery partners concerned over the potential Kremlin-White House ties and Trump’s past comments showing disdain for the alliance.