United States Secretary of Defense Jim Mattis on Thursday ruled out any military collaboration between the US and Russia, saying that the conditions just aren't correct "right now."

"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," Mattis said during a news conference at the NATO headquarters in Brussels.

Before military cooperation takes place, Russia must "prove itself" able to comply with international law, Mattis said.

WATCH: Mattis on Russia-US relations



Mattis' comments come after Russian Defense Minister Sergei Shoigu said Moscow is "ready to restore cooperation with the Pentagon."

President Donald Trump praised Russian leader Vladimir Putin during his campaign and since he's been in office, and expressed interest in restarting cooperation between the two countries. The United States halted military cooperation with Russia in 2014 after Russia annexed Crimea from Ukraine.

Islamic State



Trump has, in the past, said he would like to cooperate with Moscow in the fight against Islamic State.

Mattis, speaking at a meeting of NATO's counter-IS coalition, said he didn't think the fight against IS would end quickly, but added the United States would like to speed up the multinational campaign against the group.

When asked about the option of sending U.S. ground troops into Syria, Mattis said he hadn't yet had enough time in office to form a plan and he wants to confer with allies before moving forward.

“Once I get current…we’ll carve out where we want to go and at that point I can give you a much more steady answer. Right now I would be concerned with giving you kind of a half-baked one,” he said.

U.S. Joint Chiefs of Staff Chairman Gen. Joseph Dunford is set to meet with his Russian counterpart, Gen. Valeriy Gerasimov, in Azerbaijan later Thursday to discuss the status of current U.S.-Russia military relations.

Dealing with cyber-attacks

On the second day of the NATO ministers meeting Thursday in Brussels, NATO Secretary-General Jens Stoltenberg said they will discuss ways to combat increasingly common cyber-attacks against governments.

"Today, we will take further steps to bolster our defense. We will review progress on the deployment of our four multinational battle groups in the eastern part of the alliance. We will also address how to better counter cyber-attacks, which are becoming more frequent and complex, and we will discuss the threat from hybrid warfare and how to make our societies more resilient. So we will continue to adapt our alliance to keep our nations safe," Stoltenberg said.

Mattis expressed confidence in NATO's ability to deal with the threat from cyber-attacks, and said his colleagues responded well to his message the previous day about sharing the financial burden in defense spending.

"We thoroughly discussed the increased threats facing our alliance, and unified by the threats to our democracies I found strong alliance resolve to address these growing threats," he said.

Trump and Mattis have strongly urged other NATO nations to shoulder the financial burden of the organization.

In July, then-presidential candidate Trump caused shudders across Europe when he suggested the United States might not defend NATO allies who did not spend their share on defense.

Defense budgets

On Wednesday, Mattis warned NATO ministers Washington would "moderate its commitment" to the alliance if allies do not commit a minimum of two percent of their GDP to their defense budgets.

"America will meet its responsibilities, but if your nations do not want to see America moderate its commitment to the alliance, each of your capitals needs to show its support for our common defense," Mattis reportedly told the ministers Wednesday during a closed-door meeting.

Mattis did not say how Washington might alter its commitments to the 28-member alliance.

Among the five NATO members that meet the commitment are Greece, which pays nearly 2.5 percent, and Poland, Estonia and Britain pay just above the expected two percent. On the other end of the spectrum, Germany falls below at 1.19 percent and most, including Canada, Italy, and Spain, also fall below the mark. France pays just below two percent.

The United States pays more than 3.6 percent.