Secretary of State John Kerry said Friday that Russia had moved heavy artillery into position outside Aleppo in northern Syria, raising new concerns that a partial cease-fire will come undone.

 Russia’s military buildup, described by Mr. Kerry in a meeting with The New York Times editorial board, came on the same day that talks in Geneva aimed at finding a political resolution to the years of civil war began to break down.
After the main opposition coalition walked out, Staffan de Mistura, the United Nations special envoy for Syria, said the fragile truce was “in great trouble if we don’t act quickly.”
Mr. Kerry, who was in New York attending the signing of the Paris agreement on climate change, said he was not certain if Russia’s president, Vladimir V. Putin was sincere in his stated aims for the buildup: combating terrorism.
“We are not going to sit there and let him do his thing supporting the regime and hammer at the opposition and say, ‘This is working,’ ” Mr. Kerry said. “Obviously, we’re not stupid about it.”
Critics of the partial cease-fire deal between the United States and Russia argue that Bashar al-Assad  of Syria and his allies have been using the pause in fighting to retake territory and buttress his standing. On Friday, the opposition coalition walked out over a lack of progress in the talks as warplanes bombed heavily in northern Syria.
Asked whether the latest Russian intervention was truly aimed at fighting shared Islamist enemies or rather a means of helping Assad, Mr. Kerry said, “We have yet to discover whether they are bona fide.”
Mr. Kerry said that to try to head off renewed fighting they have agreed with the Russians to a new 24-hour monitoring system. “We’ve even proposed drawing a line, an absolute line, and saying, ‘You don’t go over there, we don’t go over here, and anything in between is fair game.’ And they are considering that, and I think we will get there in the next week or so.”
Mr. Kerry said that President Obama on Monday spoke directly to President Putin about the buildup near Aleppo, adding that he planned to speak with his Russian counterpart, Sergey V. Lavrov, later on Friday.
“We are not giving any benefit of the doubt,” Mr. Kerry said. “We have challenged them very directly by this to show in effect that they are serious about this. And if they’re not serious about it then it becomes very, very difficult to hold on to a cessation of hostilities.”
Mr. Kerry declined to discuss what options the Obama administration might pursue. Analysts suggested that the options were few and perilous and that the Obama administration had shown no appetite for wading deeper into a messy war.
Analysts said they viewed the latest American moves to pressure Russia to avoid hostilities as no more credible than past threats.
Mr. Kerry all but acknowledged that America’s options were limited should it find itself at cross-purposes with Russian forces in Syria.

Source: The New York Times, 23 April 2016