MUNICH — Russia is unlikely to respect a new accord on ceasing hostilities in Syria given the aggressive hand it has played there and the advantage it has gained by using armed force, a senior ally of the German chancellor said Sunday.

The blunt assessment from Norbert Rottgen, chairman of the foreign affairs committee in the German Parliament, came at an annual security conference here that usually focuses on the trans-Atlantic alliance.

Rottgen’s comments followed biting criticism from Senator John McCain over the US-Russian accord, announced on Friday, to get aid into some Syrian regions and implement a truce plan for the devastated country.

The two criticisms came against the backdrop of news from Syria that no aid trucks had yet moved toward needy regions there and illustrated how thoroughly the Middle East chaos had dominated the conference.

The general mood was bleak, overshadowed by the failure to quell the five-year conflict in Syria earlier, the Russian military intervention there and the spread of Islamic terrorism. Europe’s failure to unite around a response to more than 1 million migrants and refugees and Russian talk of a looming new Cold War added to the glum atmosphere.

Discussion at the conference on Sunday focused on the plan to cease hostilities in Syria within a week and recriminations about the failure of the Obama administration, and others, to have intervened more forcefully or to have anticipated the spreading turmoil.

McCain, Republican of Arizona and chairman of the Senate Committee on Armed Services, said Sunday he wished he could regard the truce plan as a breakthrough.

More likely, he said, it was a move that “permits the assault on Aleppo to continue for another week,’’ thus locking in Russian military superiority and allowing the forces of President Bashar Assad of Syria to take back more territory from rebels.

McCain, who traditionally heads the congressional delegation to Munich each year, suggested that Vladimir Putin, the president of Russia, was relying on ever more powerful shows of force to reassert his country’s role as a dominant global power. “His appetite is growing with the eating,’’ McCain said, adding, “We have seen this movie before in Ukraine.’’

Rottgen was also strongly critical of Russia. He urged Western powers to learn from events in Syria, particularly in regard to Europe’s security. He said that more needed to be spent on defense and that Europe, while still needing the United States, should not rely on America for its safety.

“Russia has gained the upper hand in the region and this is by historical measure a novelty,’’ Rottgen said. “They have done so by the use of armed force.’’

“Russia is determined to create the facts on the ground,’’ Rottgen said, “and when they have accomplished this, they will invite the West to fight a common enemy, that is ISIS.’’

He said Russia’s approach had disqualified it as a partner in the fight against the Islamic State, and echoed the British foreign secretary, Philip Hammond, who said the development in Syria “depends on Russia.’’

Asked what Germany had done or gotten wrong in Syria, Rottgen said that “we thought we could afford to focus only on Russia and Ukraine,’’ failing for instance to try to create a humanitarian zone of some kind where Syrians could shelter within their country.

In a separate development Sunday, Turkey said it shelled positions held by the main Kurdish militia in northern Syria for a second day, the Associated Press reported.

The action drew condemnation from the Syrian government, whose forces are advancing against insurgents in the same area under the cover of Russian airstrikes.

Turkey’s state-run Anadolu Agency said Turkish artillery units in the southern province of Kilis fired at Kurdish fighters in the Syrian town of Azaz in Aleppo province, saying it was in response to incoming Kurdish fire.

Turkish troops have shelled areas under the control of Syria’s main Kurdish faction, the People’s Protection Units, known as YPG, in the past. But Ankara appears increasingly uneasy over the group’s recent gains in northern Syria.

‘‘Turkey has responded in this manner in the past,’’ said Turkey’s Deputy Prime Minister Yalcin Akdogan. ‘‘What is different is not that Turkey has responded in such a way but the fact that there are different movements in the region. The YPG crossing west of the Euphrates is Turkey’s red line.’’

The YPG is the main fighting force of Syrian Kurds and a key ally of the US-led coalition battling the Islamic State group. Turkey, which is also in the alliance, considers it an affiliate of the Kurdistan Workers’ Party, or PKK, which has waged a decades-long insurgency against Ankara.

A coalition of Kurdish-led Syrian fighters known as the Syrian Democratic Forces recently seized a number of villages near Turkey’s border. Ankara appears concerned they could reach the opposition stronghold of Azaz, which is home to a major border crossing that has been controlled by militants since 2012.

France on Sunday called for an immediate end to airstrikes by Syria and Russia against insurgents opposing the Assad government, and also demanded a a halt to the Turkish shelling of Kurdish areas.

Some speakers at the Munich conference singled out the Obama administration for failing to act in 2013 after President Obama said use of chemical weapons by Assad would cross a “red line’’ that demanded US action.

Back then, Russia again intervened, using its influence to get Assad to agree to put all chemical weapons under United Nations supervision for removal and destruction.

McCain said that that move had destroyed Washington’s credibility, particularly with Saudi Arabia, who he claimed had planes ready to fly air raids on Syria when Obama accepted the Russian-backed plan on chemical weapons.