NEWPORT, Wales (CNN) -

NATO members agreed Friday to form a "spearhead" force of several thousand land troops ready to deploy within a few days, NATO chief Anders Fogh Rasmussen said, as the trans-Atlantic alliance grapples with the threats posed by Russia's interference in Ukraine and the rise of ISIS in Syria and Iraq

The troops would be backed by air, sea and special forces support, he said, with a command and control center and extra equipment in Eastern Europe.

"This decision sends a clear message: NATO protects all allies at all times," Rasmussen said on the second day of a NATO summit in Newport, Wales.

"And it sends a clear message to any potential aggressor: Should you even think of attacking one ally, you will be facing the whole alliance."

The new readiness action plan, which includes proposals for more short notice exercises, is intended to help NATO respond swiftly to Russian aggression and other international conflicts.

"In these turbulent times, NATO must be prepared to undertake the full range of missions and to defend allies against the full range of threats," Rasmussen said.

He said NATO members also "stand ready to assist Iraq" in its fight against Islamist extremists if Baghdad asks for help.

But pressed by reporters on exactly what aid NATO would offer, Rasmussen toned down his remarks, saying NATO is prepared to consider a "defense capability building mission" in Iraq.

President Barack Obama said Friday that "there's great conviction that we have to act as part of the international community to degrade" and ultimately destroy ISIS jihadists that pose a long-term threat to member countries.

The United States has sent military advisers to Iraq to help that country combat ISIS.

Canada -- a NATO member -- said Friday it also will send "several dozen" troops to Iraq to help advise that country's government on fighting ISIS, Prime Minister Stephen Harper's office said.

Responses to threats posed by Russia's interference in Ukraine and the rise of ISIS in Syria and Iraq were at the heart of discussions of the alliance's meeting in Wales.

Obama rebuffs Russian warnings on NATO, Ukraine

Russia's annexation of Crimea and involvement in the unrest in eastern Ukraine have alarmed NATO members such as Poland and the Baltic States.

A rapid-reaction force would give those nations more security amid Moscow's deteriorating relationship with the West. U.S. officials have stressed that any force would be defensive in posture and not a provocation to Russia.

Obama said Friday at the end of the summit that "Russia's aggression against Ukraine threatens our vision of a Europe that is whole, free and at peace."

He also rebuffed Russian warnings against NATO membership for Ukraine, saying membership in the alliance remains "open to nations that meet our high standards."

The comments echoed Rasmussen's earlier remarks.

"No third party has a veto" on new members joining NATO, Rasmussen said.

Also Friday, Prime Minister David Cameron said the United Kingdom would be willing to contribute 3,500 personnel to the new NATO force.

Edward Lucas, a senior editor at The Economist in London, said it's important to get a rapid-reaction force "that is pre-authorized, a bit like a pre-authorized credit card, so that if there is a crisis, it can be deployed very quickly by NATO military commanders."

Otherwise, activation of the force could get bogged down in political discussions, Lucas told CNN.

Greater spending

The allied nations also agreed to work toward increasing defense spending over the next decade as part of their NATO commitments, Rasmussen said.

The goal: 2% of gross domestic product, 20% of which will go toward equipment, over the next decade.

The Ukraine crisis is a major reason for the decision, he said. While he said Russia has increased defense spending by 50% in the last five years, NATO nations have cut back on average 20%.

"Russian aggression against Ukraine is a wake-up call, and I think this is exactly what has led capitals in NATO allied nations to reconsider defense investments," Rasmussen said. "Because it is now obvious that we cannot take our security for granted, and we will have to invest more in our defense and security."

The recent revival of a Russian threat in Eastern Europe has upended some of the assumptions that had underpinned NATO's earlier expansion in the region.

"This is the first time since the end of World War II that one European country has tried to grab another's territory by force," Rasmussen said Thursday. "Europe must not turn away from the rule of law to the rule of strongest."

Lucas pointed out that when NATO first brought Eastern European countries such as Poland and Hungary into its fold in the late 1990s, it decided to regard Russia as a friend rather than a threat, forgoing plans to defend the new member states.

"The whole idea was that NATO would be in partnership with Russia to deal with other security issues," he said. "That's changed because Russia didn't like that arrangement. Russia has bullied its neighbors."