MUNICH, Germany -- World powers wrestled with the challenges of a "bleak" global security environment at a conference clouded by Russia's vow to continue bombing targets in Syria despite a deal on a cessation of hostilities.
Senior officials opening the Munich Security Conference on February 12 welcomed the agreement, which was reached hours earlier at a meeting on Syria in the German city that broke up after midnight.
But Western and Middle Eastern leaders warned that the agreement will only work if it is implemented on the ground, and worried that Russia's refusal to halt air strikes could scuttle the chances of a negotiated solution to the five-year war.
"If Russia does not end its strikes on Western-backed Syrian opposition forces, a cease-fire reached by major powers will not hold and humanitarian access will not be effectively secured," Turkish Foreign Minister Mevlut Cavusoglu said on February 12.
Cavusoglu also accused Russia of targeting schools and hospitals as part of its bombing campaign, and blamed Moscow for a wave of tens of thousands of people who have arrived at the Turkish border in the past week.
Hundreds of thousands of Syrians have been killed in the conflict, which began with President Bashar al-Assad's crackdown on protesters and flared into civil war pitting government forces against opponents ranging from Western-backed rebels to Islamic State (IS) militants.
Opening the Munich conference, its chairman, Wolfgang Ischinger, called the Syria war a "full-fledged regional conflict" that -- along with the death and destruction -- has driven the biggest wave of refugees since World War II.
"The global strategic environment is bleak," Ischinger said at the conference, whose attendees included U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov, as well as Russian Prime Minister Dmitry Medvedev.
"The international order, in my view, is in its worst shape since the end of the Cold War," he said. "Overwhelmed and helpless guardians are faced with increasingly boundless crises and empowered and reckless spoilers."
Speeches at the security conference on its first day focused largely on the threat from the extremist group IS, which seized swaths of Iraq and Syria in 2014 and has terrorized the people in its path.
Speakers also talked about how to handle the refugee crisis confronting the Middle East and Europe, which is deeply interlinked with IS and the Syria war and has undermined unity in the West at a time when it faces a persistent challenge from Russia on its eastern flank.
The defense chiefs of core EU members Germany and France welcomed the agreement on a cessation of hostilities, but said it must be implemented.
French Defense Minister Jean-Yves Le Drian said the deal will only be effective "if air strikes by Syrian and Russian forces stop." Another attendee, King Abdullah of Jordan, said that "the killing in Syria has to stop...if we are to find a solution."
The White House said the agreement is significant, but that work is far from over in the peace talks.
"In the coming days, we will be looking for actions, not words, to demonstrate that all parties are prepared to honor their commitments," White House spokesman Eric Schultz told reporters in a briefing on February 12.
The agreement for a truce is intended to allow humanitarian aid to reach people in Aleppo, the target of a major Russian-backed government offensive in the past weeks, as well as other besieged Syrian communities nationwide.
However, the agreement allows attacks to continue against groups designated as terrorist organizations by the UN Security Council, including IS (also known as Daesh) and the Al-Nusra Front, which is Al-Qaeda's affiliate in Syria.
Western diplomats have said privately that they worry Russia might seek to continue bombing Western-backed opposition forces despite the peace deal by claiming the attacks are against "terrorist" groups excepted from the accord.
Russian Foreign Minister Sergei Lavrov was quoted by AFP as saying that "the truce does not apply to terrorists, and that is stated in today's document." He added, "The military operation against them will be continued."
Moscow and Damascus have often broadly labeled Syria's many rebel groups as terrorist organizations, and Western officials say a substantial majority of Russia's air strikes have targeted groups other than IS.
Russian President Vladimir Putin has said the Russian campaign will go on as long as the Syrian government offensive, and Moscow has adamantly insisted that Assad's exit from power cannot be a precondition for a solution.
Syrian President Bashar al-Assad, meanwhile, vowed on February 12 to retake the "whole country," saying that just because negotiations are taking place, "it does not mean that we stop fighting terrorism. The two tracks are inevitable in Syria."
Western nations and Syrian neighbors such as Saudi Arabia want Assad out and say there can be no lasting solution if he stays in power.
Speaking to reporters in Munich after a meeting with Lavrov, NATO Secretary-General Jens Stoltenberg accused Russia of "mainly target[ing] opposition groups and not ISIL," using another abbreviation for IS. "Air strikes of Russian planes against different opposition groups in Syria have actually undermined the efforts to reach a negotiated, peaceful solution."
Stoltenberg said that the cessation of hostilities agreement "has to the first step toward a lasting cease-fire" and that the important thing now is to see it implemented on the ground.
British Foreign Secretary Philip Hammond said the humanitarian truce "will only succeed if there is a major change of behavior by the Syrian regime and its supporters."
A key rebel coalition, the Higher Negotiating Committee, said it welcomed the deal "in principle." But the Saudi-based grouping said, "We want deeds, not just sayings."
The cessation accord was struck by the United States, Russia, and a dozen other countries composing the International Syria Support Group (ISSG).
Announcing the accord, Kerry said the truce is a "pause" and not a formal "cease-fire."
He said that the ISSG members had agreed that formal negotiations to establish a more lasting peace should resume in Geneva as soon as possible.
Representatives of the 17 ISSG countries were meeting in Geneva on February 12 to hold talks on how to ensure humanitarian access to needy communities across Syria.
Jan Egeland, the head of the Norwegian Refugee Council who will chair the UN meeting in Geneva, said the accord "could be the breakthrough we have been waiting for to get full access to desperate civilians inside Syria."
But he said the deal "requires that all those with influence on all sides of the conflict to put pressure on the parties."
Western officials worry that gains made by government forces since Russia launched an open-ended bombing campaign on September 30 may have reduced the incentive for Moscow ally Assad to seek a diplomatic solution.
Meanwhile, prospects for formal Syrian peace talks to resume in Geneva remain uncertain.
UN envoy for Syria Staffan de Mistura said plans to reconvene the talks are still "cloudy" but that he hopes they will resume on February 25.
The latest round of Syrian peace talks began in Geneva on January 29 but derailed almost immediately over opposition groups' anger at escalating Syrian government and Russian air attacks on rebel areas around Aleppo.