Rebel-backer Turkey has held several rounds of talks with regime ally Russian Federation aimed at averting an assault on Idlib, but Moscow dubbed the region a "pocket of terrorism".
Worldwide calls mounted on Wednesday (Sep 5) to avoid a "massacre" by regime forces in Syria's last rebel-held province of Idlib, two days before a summit between key powers backing the government and opposition.
The United Nations and aid groups have warned a military campaign could spark one of the worst humanitarian catastrophes in a war that has already killed more than 350,000 people and displaced millions.
Pompeo and Cavusoglu "agreed that any Assad regime military offensive in Idlib would be an unacceptable, reckless escalation of the conflict in Syria", said U.S. State Department spokeswoman Heather Nauert.
Germany would consider boosting humanitarian assistance for Syrian refugees in countries neighbouring state in the case of an all-out regime offensive in the northern region of Idlib, said Maas.
The countryside around Jisr al-Shughour in the west of the enclave was also the main target for Tuesday's air strikes, rescue workers, a rebel source and the British-based Observatory said.
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Turkey, Russia and Iran past year designated Idlib a so-called "de-escalation zone", but that deal did not cover former Al-Qaeda affiliate HTS.
"We know that the Syrian armed forces are getting ready to solve this problem", President Vladimir Putin's spokesman Dmitry Peskov said, calling Idlib a "pocket of terrorism".
"The United States is closely monitoring the situation in Idlib province, Syria, where millions of innocent civilians are under threat of an imminent Assad regime attack, backed by Russian Federation and Iran", the White House statement reads.
Its president, Tayyip Erdogan, was quoted by a Turkish newspaper saying an attack on Idlib would be "a serious massacre" and he hoped for a positive outcome from a summit with Russian and Iranian leaders on the matter on Friday.
The human rights group Amnesty International said in a statement on Wednesday that the lives of "millions of people in Idlib are now in the hands of Russia, Turkey and Iran", and urged all parties not to attack civilians.
Israel has fired more than 800 missiles and mortar shells at targets in Syrian territory over the a year ago and a half, according to the statement.