NATO defense ministers have agreed to moves to protect the alliance and its allies against increased threats from Russia and to bolster combat readiness by easing the transport of troops across Europe in the event of a crisis.

The measures agreed to on June 7 in Brussels would reinforce NATO's presence in a potential European crisis with the deployment of 30 troop battalions, 30 squadrons of aircraft, and 30 warships within 30 days -- the so-called "Four 30s" plan.

NATO defense ministers also set staffing levels of more than 1,200 personnel for new commands covering the Atlantic Ocean, handling logistics during any conflict on mainland Europe. They will be based in Norfolk, Virginia, and Ulm, Germany.

Full details were not revealed of the U.S.-designed plan, set to be in place by 2020.

"We have decided further steps to strengthen our shared security and boost defense and deterrence against threats from any direction," NATO Secretary-General Jens Stoltenberg told reporters.

He said the two commands will help "ensure we have the right forces in the right place at the right time."

He said a day earlier that the move was not "about setting up or deploying new forces -- it is about boosting the readiness of existing forces across each and every ally," Stoltenberg said.

The Brussels ministers meeting was designed to help finalize an agenda ahead of a full NATO summit of leaders that will take place in five weeks.

"The decisions we have taken today pave the way for a successful summit in July, with more investment, more equitable burden-sharing, and a strengthened defense posture," Stoltenberg said.

U.S. President Donald Trump, who has criticized NATO allies for perceived shortfalls in defense spending, is scheduled to attend the summit.

The United States and European allies also have differences over trade issues and the U.S. decisions to pull out of the Iran nuclear deal and the Paris climate accord.

But Stoltenberg said the United States remained committed to European defense.

"Many ministers highlighted the importance of NATO unity and that we have to stay united, especially when we see that Russia tries to divide us," Stoltenberg said.

"We have disagreements between NATO allies, but we stand together in NATO when it comes to the core task of NATO...to protect each other," he added.

Relations between Moscow and NATO remain at their lowest levels in years, severely damaged in 2014 following Russia’s annexation of Ukraine’s Crimea Peninsula and its aid for separatists in eastern Ukraine.

Russia’s support for Syrian President Bashar al-Assad and North Korea’s Kim Jong Un have also helped raise tensions between East and West.

Meanwhile, Stoltenberg unveiled higher expenditure estimates for NATO in 2018, saying defense spending by European governments, Turkey, and Canada is expected to rise by 3.82 percent.

If fulfilled, it would mark the fourth year in a row of hikes and would represent an $87.3 billion increase since 2015.

With reporting by AP, Reuters, and dpa