Yasar Guler and Joseph Dunford held the bilateral meeting on the sidelines of the NATO Military Committee Conference in Slovenia's Ljubljana.
No immediate information on casualties from the strike on Rahma hospital in Tal Mannas.
A pilot who ejected from the plane was captured, says Syrian Observatory for Human Rights after militants shoot down a regime warplane in Idlib province.
The push towards Khan Shaykhun threatens to encircle the last remaining pocket of opposition and rebel territory in neighbouring Hama province, including the towns of Morek, Kafr Zeita and Latamneh.
The capture of Habeet opens up an approach to southern regions of Idlib, which is home to some three million people, many of them displaced by fighting in other parts of the country.
The explosive-rigged vehicle detonated in Al Qahtaniya, a town in Hasakeh province, says the Syrian Observatory for Human Rights, a Britain-based monitor.
Syrian regime has approved "a ceasefire in the de-escalation zone in Idlib starting from tonight" on the condition militants and rebels withdraw forces and weaponry from a buffer zone as per a September accord struck in the Russian city of Sochi.
The attacks targeted residential areas in the towns of Jisr al Shughur, Khan Shaykhun, Maar Shoreen, Hantoteen and Ain al Bardeh in Idlib province, according to an Anadolu Agency correspondent on the ground.
Implementation of a 2012 roadmap to UN-supervised elections in Syria has been discussed by US and Russian diplomats, says Ambassador James Jeffrey amid ongoing attacks in north-west Syria.
The Syrian Observatory for Human Rights and White Helmets Civil Defence say scores of people have been killed since the Assad regime and its Russian ally renewed violence in Idlib and Hama provinces 13 days ago.
Civilians in densely populated areas have been caught up in joint Russian and Syrian regime air raids. Many say they have no choice but to flee for their lives.
The Assad regime has stepped up deadly attacks in Idlib and Hama. There could be a catastrophe if the bombing intensifies as the regime attempts to take the last remaining rebel stronghold.
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