NATO Secretary-General Jens Stoltenberg says that the alliance has reached a "defining moment for our security" and that its summit in Poland this week will confront head-on the challenges of an increasingly "dangerous" world.
Stoltenberg's comments at a joint news conference with Polish President Andrzej Duda came ahead of a two-day NATO gathering starting on July 8 during which Moscow's actions in Eastern Europe will be a focus of discussion.
The alliance's relations with Moscow reached their lowest point since the Cold War following Russia's military seizure and annexation of Ukraine's Crimean Peninsula in 2014 and the ensuing war between Kyiv's forces and Russia-backed separatists in eastern Ukraine.
"The world is a more dangerous place than just a few years ago," Stoltenberg said. "NATO is responding with speed and with determination."
He added that during the summit, NATO "will take new major steps to further modernize our collective defense and deterrence and to project stability beyond our borders."
In the wake of Russia's actions in Ukraine, NATO has moved to reinforce its support for its eastern members that were under Moscow's domain during Soviet times and remain wary of the Kremlin's intentions in the region.
NATO is expected to agree in Warsaw to the deployment of battalions of up to 1,000 troops in Poland and in each of the three Baltic states: Estonia, Lithuania, and Latvia.
The plans have angered Moscow, which has long accused NATO of stoking hostilities with its eastward expansion over the past two decades, a charge the alliance rejects.
In an interview published in the Russian newspaper Kommersant, Russia's ambassador to NATO, Aleksandr Grushko, accused the alliance of having a "confrontational agenda" and warned that Russia would take countermeasures.
Kerry In Kyiv
In a show of support for Ukraine one day before the summit, U.S. Secretary of State John Kerry met with President Petro Poroshenko in Kyiv and pledged that U.S. sanctions against Russia will remain in place unless Moscow fulfills its obligations under the Minsk agreement reached last year in an effort to bring lasting peace to Ukraine.
Kerry and Poroshenko discussed progress toward implementing the deal and ending a conflict that has killed more than 9,300 people in eastern Ukraine since April 2014.
U.S. officials say Ukraine has completed most of its obligations under the Minsk agreement that relate to providing the east -- where the separatists hold parts of the Donetsk and Luhansk regions, also known as the Donbas -- with greater autonomy.
But the officials say Moscow and the separatists have not done their part on key security issues such as ensuring a cease-fire, withdrawing heavy weapons, providing full access to Organization for Security and Cooperation in Europe (OSCE) monitors, and restoring Ukrainian control to border crossings with Russia.
"Ukraine is making a good-faith effort to implement Minsk," Kerry said, adding that the same message was relayed by President Barack Obama to Russian President Vladimir Putin during their phone call on July 6.
"President Putin indicated that he does have a desire to see this process move forward, as does President Obama," Kerry said, adding that the international community would welcome proof of Russia's choosing "the path to de-escalation and full implementation of Minsk."
Kerry lauded Ukraine's efforts at judicial, legislative, and economic reforms, as well as a new anticorruption program.
He also announced that the United States will provide nearly $23 million in additional humanitarian aid to help people affected by the crisis in eastern Ukraine.
Poroshenko, who has been invited to the NATO summit, stressed Ukraine's demands for security.
"There cannot be effective progress without comprehensive and sustainable security," he said. "We insist on decisive implementation."
While there is little prospect of Ukraine joining NATO in the near future, Poroshenko indicated the alliance must keep its doors open despite fierce Russian opposition.
He said Ukraine expects that the Warsaw summit to uphold "the positions adopted at the NATO summit in Bucharest [in 2008] -- the key of which is that NATO's doors are open to any European country."
Kerry said that during the summit the NATO-Ukraine Commission, which is a decision-making body responsible for developing the mutual relationship, will hold a special meeting at the level of heads of state.
Kerry's visit to Kyiv followed high-level meetings in Georgia, where he signed an agreement to boost U.S. military cooperation. Georgia's NATO aspirations were a chief catalyst for the five-day war in 2008 in which Russian forces drove deep into the South Caucasus country.
Merkel: Dialogue Backed By Firmness
German Chancellor Angela Merkel, meanwhile, defended NATO's plans to bolster its presence in Central and Eastern Europe amid tensions with Russia over Ukraine, saying the Kremlin was to blame for the West's loss of trust in Moscow.
Merkel told the German parliament on July 7 she was ready to offer Moscow her "outstretched hand for dialogue" on July 7, saying that Germany wants a constructive relationship between Russia and NATO.
But she warned that dialogue has to be backed by firmness.
"This means deterrence and dialogue, the clear commitment to solidarity with our partners in the alliance...and an outstretched hand for dialogue," Merkel said.
She told lawmakers it was not enough to be able to quickly relocate troops in emergencies.
"The alliance needs to have a stronger presence in the Baltics and in Poland," Merkel said.
Merkel told lawmakers that Germany will make "a substantial contribution" to NATO's deployment plans in Eastern Europe.
The NATO-Russia Council, which was for two years dormant until a reportedly acrimonious effort to revive regular consultations in April, will meet at the ambassadorial level at the alliance's headquarters in Brussels on July 13.
With reporting by Reuters, AP, and dpa