Russia has warned the United States that Moscow’s patience is running thin over Washington’s refusal to target Takfiri militants fighting against the Syrian government.

Last week, US Secretary of State John Kerry warned Russia that America’s patience on the issue of Syrian President Bashar al-Assad's future was running out. Pentagon Press Secretary Peter Cook also said US military officials had “expressed strong concerns” about Russia’s airstrikes against US-backed militants, “which included forces that are participants in the cessation of hostilities in Syria." Russia has denied the US claim.

Syria is currently observing a ceasefire brokered by Russia and the US, which entered into force on February 27. The truce, which was reached between the Syrian government and dozens of militant groups operating in the country, does not apply to the Daesh and al-Nusra Front terrorist groups.

However, renewed violence in some parts of Syria, particularly around Aleppo, has left the ceasefire in tatters in recent weeks and torpedoed peace talks on the conflict.

Valery Gerasimov, the head of Russia’s General Staff

On Monday, Valery Gerasimov, the head of Russia’s General Staff, said although the Russian Defense Ministry has been giving the coordinates of Daesh and al-Nusra militants to the US for three months, the US-led coalition is still “undecided” about whether to target those positions.

"It is us, not Americans who are losing patience concerning the situation in Syria. We are fully meeting our commitments and agreements on securing the ceasefire and national reconciliation in Syria," Gerasimov said.

He added that “the American side always has problems with the ‘opposition under its control," the Tass news agency reported.

Moscow has long insisted that the so-called moderate opposition groups in Syria should leave the areas held by Daesh and al-Nusra terrorists targeted in the Russian air campaign. Claiming it is unable to remove the opposition groups, Washington, however, has called on Moscow not to carry out airstrikes against the al-Qaeda-affiliated al-Nusra Front terrorist group.

“As a result, terrorists are actively restoring their strength and the situation is escalating again," Gerasimov said.

A Syrian man walks past destroyed buildings in the city of Aleppo on May 2, 2016. ©AFP

"In their opinion missile bombardments of Syrian government troops and communities by militants should be considered by all as ‘insignificant violations’ of the ceasefire. But the Syrian military's proportionate responses to the militants are at once declared as disproportionate strikes on the opposition," he added.

Referring to a deconfliction contact center set up between the two countries, the Russian official said, "Whenever we hear claims from the Pentagon we use communication lines not professionally, it gets clear that they are either ignorant of the existing channels of interaction or get wrong information."

The US and some of its Arab allies have been conducting airstrikes against alleged Daesh position in Syria since September 2014.

Russia launched its air campaign against Daesh and other terrorist groups upon a request by Damascus the next year. Russian military planes and helicopters are providing support to the Syrian army's ground operations against extremists.

A Russian Sukhoi Su-35 bomber lands at the Russian Hmeimim military base in Latakia province, in northwestern Syria, on May 4, 2016. ©AFP

Syria has been gripped by foreign-backed militancy since March 2011.

UN special envoy for Syria Staffan de Mistura estimates that over 400,000 people have been killed in the conflict, which has also displaced over half of the Arab country’s pre-war population of about 23 million.