The strain is likely to grow more acute as the government depends on helicopter gunships to extend its reach to parts of the country rendered impassable to logistics convoys and even armored vehicles by the rebels' improvised bombs.
A Labour source said that, given teenagers have a "tremendous vested interest in whether or not we stay in the EU or leave", there could be a strong appetite for amending the EU referendum bill in the Lords, even if Labour and the SNP fail to recruit the relatively small number of Tory rebels they would need to defeat the government in the Commons.
Although a growing body of evidence, including interviews with Russian soldiers, indicates that Moscow has sent active-duty troops and equipment to support the pro-Russia rebels over the past year, the president, Vladimir Putin, continues to deny his forces' participation in the conflict.
Moscow has pushed to have pro-Russia rebels included in national unity talks, but Ukrainian leaders say they will not negotiate with "terrorists".
He told the Lowy Institute the milestone was proof the west's diplomatic pressure and sanctions against Russia – which is backing separatist rebels in the east – were bearing fruit.
He said he was joining the rebels because of the "brutal" crackdown on dissent that has claimed the lives of thousands of Syrians.
But LifeNews, a Russian website known for its access to the Kremlin's security services, reported on Sunday that Kiev's forces were shelling airport building and said rebels had repulsed four "mass attacks" by Ukrainian foot soldiers and 15 tanks in the morning.
It said the rebels were from the al-Qaida linked Jal-Nusra Front and included non-Syrians.
While we bomb Isis, Assad spares it and prefers to barrel-bomb Syrian civilians in the pockets of territory still controlled by the rebels fighting his rule.
Bombs planted by rebels exploded at a school building occupied by security forces and pro-government militias in Damascus, activists and rebels said.
It has said the rebels, who are backed by both western and Arab countries, are also guilty of committing war crimes.
