If Turkish pro-government forces advance, they could come into contact with USA troops stationed in region.
Turkey says Sinjar has turned into a PKK headquarters. "If you can not handle it, then we may suddenly enter Sinjar one night and clear out the PKKs there".
Although Turkey recently captured Afrin, Erdogan claims Operation Olive Branch will continue.
Syria's seven-year war has killed more than 350,000 people and displaced more than half the country's population either inside Syria or overseas - including more than three million to Turkey. Ankara has accused the USA of not fulfilling a promise to move Syrian Kurdish fighters out of Manbij.
Turkish Prime Minister Binali Yildirim was holding talks with the Iraqi government, Erdogan added.
"Politically, though, it would be very hard to accomplish", he said.
Turkish troops and their rebel allies swept into the north-west Syrian town of Afrin yesterday, the culmination of an eight-week campaign to drive the Kurdish YPG fighters from the region.
Such an insurgency could prove to be "a big thorn" for the USA military operation in Syria, Heras said.
Turkish leader vows wider offensive against Kurdish militia
Before the Turkish assault, the Kurdish-controlled region - known as Rojava - ran across large swathes of Kurdish-majority parts of north and northeast Syria.
In a statement, the Turkish General Staff said an improvised explosive blew up and martyred three soldiers and injured three others in search operations. Turkey views the Syrian Kurdish militiamen as terrorists because of links to Kurdish insurgents fighting inside Turkey.
"Afrin is one of the most strategic areas of northwest Syria".
"Our General Staff was in contact with the International Committee of the Red Cross, the United Nations and the Turkish Armed Forces allowed and protected the passage of a humanitarian aid convoy to Afrin city center", Hürriyet Daily News cited Kinik as saying. Federica Mogherini told reporters in Brussels that worldwide efforts in Syria should be aimed at "de-escalating the military activities and not escalating them".
Adil Siraz, the Disaster and Emergency Management Authority (AFAD) provincial director in southern Turkey's Kilis province, near Syria, said that AFAD teams have been racing to serve the areas cleared of terrorists.
Thousands fled as the rebels, mostly fighters opposed to Syrian President Bashar al-Assad, celebrated their victory by destroying the statue of Kurdish hero Kawa.
The US State Department also expressed concern over the humanitarian ramifications of the Turkish operation in Afrin.
Speaking to Anadolu Agency, Tekin Baser, Kecioren's vice mayor, said that so far they have renovated six schools in Afrin.
He said fear of people taking over their homes has also fuelled violent sentiments among Kurds.More news: Crude Prices Jump Amid Saudi-Iran Tensions