Anders Fogh Rasmussen, the NATO secretary-general, has said that the military alliance has agreed a readiness action plan to strengthen the organisation's capabilities, including the establishment of a rapid-action force.
The development comes on a busy day in terms of diplomacy for the Ukraine crisis, with NATO leaders holding the second day of a summit in Wales and ceasefire talks taking place in the Belarusian capital.
Speaking at a news conference in Newport, Wales, Rasmussen said: "We agreed to form a spearhead force to be able to be deployed in short time."
"This will include land troops ready to deploy in a few days supported by air and sea."
He added that NATO will also form a command centre in eastern allied territory.
In what he said was a message to potential aggressors, Rasmussem said the measures were being implemented: "So we can deal swiftly and firmly with threats.
"If you threaten one ally, you will face the whole alliance … NATO remains strong ready and responsive for future challenges wherever they may come from."
Though not mentioned, the announcement was interpreted by observers as a message to Russia, which NATO has accused of aiding pro-Russian separatists in Ukraine's east.
On Friday, a ceasefire between Ukrainian military forces and the rebels was agreed at talks on a new peace plan to end the five-month conflict that the UN says has killed an estimated 2,600 people.
As pressure on Moscow ramps up, the White House said that key NATO leaders had agreed during the meeting that Russia should face increased sanctions for its actions in eastern Ukraine.
|Al Jazeera's Harry Fawcett reports from Mariupol
Ambassadors of the EU member states were also gathering in Brussels to discuss further sanctions on Russia.
Meanwhile, Russia has banned confectionery imports from two Ukrainian firms, Konti and AVK, Russia's consumer watchdog said on Friday.
Rospotrebnadzor said in a statement that both companies had violated the law on consumer rights protection.
The diplomatic developments came after a week in which the rebels scored major victories with what NATO says is the open support of thousands of Russian troops and armour.
The rebels have made substantial advances against Ukrainian forces, including opening a new front along the Sea of Azov.
That offensive has raised concerns the rebels are aiming to seize Mariupol, a major port of about 500,000 people, and create a land corridor between Russia and Crimea, the Black Sea peninsula that Russia annexed in March.