NATO urges Russia withdrawal

Rasmussen said at the summit in Wales on Thursday that NATO urges Russia "to end its illegal and self-declared annexation of Crimea."

"We call on Russia to pull back its troops from Ukraine and to stop the flow of arms, fighters and funds to the separatists," Rasmussen said during a meeting with Ukrainian President Petro Poroshenko. "We call on Russia to step back from confrontation and take the path of peace."

The meeting, being held at the Celtic Manor golf resort just outside of the Welsh city of Newport, kicked off with a ceremony in which Rasmussen and the national leaders paid tribute to soldiers killed while serving in NATO missions abroad.

German Foreign Minister Frank-Walter Steinmeier expressed optimism during the summit that a de-escalation of violence was on the horizon in Ukraine.

"It would be good and it is urgently necessary for progress to be made in these direct talks here," Steinmeier told reporters.

Ahead of the summit, US President Barack Obama and British Prime Minister David Cameron sharply criticized Moscow.

"Russia has ripped up the rulebook with its illegal, self-declared annexation of Crimea and its troops on Ukrainian soil threatening and undermining a sovereign nation state," the two leaders wrote in a joint statement released on Thursday.

Middle East concerns

Obama also met with Jordan's King Abdullah II. Jordan is a close US ally in the Middle East, where the US is currently combating militants from the self-proclaimed "Islamic State" (IS) in Iraq.

Before Thursday's meeting began, Rasmussen said the international community "has an obligation to stop the Islamic State from advancing further" and that NATO would be willing to consider an Iraqi request for assistance.

"I'm sure that if the Iraqi government were to forward a request for NATO assistance, that would be considered seriously by NATO allies," he said.

Uncertainty over Afghanistan

Rasmussen also touched on the political situation in Afghanistan, calling on Afghan leaders to resolve their presidential election and reach an agreement that would allow NATO soldiers to remain in the country beyond 2014.

The secretary general said NATO was ready to provide assistance and funding to Afghanistan, but first needed the country to end its political stalemate. Afghanistan's defense ministry represented the country at the NATO summit, as the results of the Afghan presidential election are not yet final.

The rival candidates, Ashraf Ghani and Abdullah Abdullah, told NATO in a joint statement they were committed to forming a national unity government after the election is resolved.

dr/sb (Reuters, AP, AFP, dpa)