New US Secretary of State John Kerry is visiting Turkey for talks expected to focus on the conflict in Syria.
The two Nato allies both oppose Syrian President Bashar al-Assad, but differ on how best to support the opposition.
On Thursday Mr Kerry promised direct aid to Syrian rebels in the form of food and medical supplies, but not the weapons they say they need to win.
Turkey has taken in more than 200,000 Syrian refugees and has been hit by deadly cross-border shelling.
Tension
Turkey wants the Syrian rebels to win the war as soon as possible and will be keen to convey its sense of frustration to Mr Kerry, the BBC's James Reynolds in Istanbul says.
The fighting and flow of refugees has caused high tension along Turkey's 900km (560 mile) border with Syria.
The US and other Nato allies have deployed Patriot missile interceptors to repel any possible attack by missiles or aircraft from Syria.
Turkish Prime Minister Recep Tayyip Erdogan has been outspoken in his support for Syrian rebels and has advocated the creation of a buffer zone inside northern Syria to protect people fleeing the fighting.
Turkey began massing troops along the frontier in June last year after Syria shot down a Turkish reconnaissance jet off its coast.
In October the Turkish army fired on military targets in Syria in retaliation for cross-border mortar fire,
The rebel Free Syrian Army is thought to receive weapons and other supplies from Turkey.
But the US has refrained from arming the rebels, in part because of concerns the weapons could eventually fall into the hands of Islamist militants who might attack its interests.
On Thursday in Rome, Mr Kerry promised an additional $60m (£40m) in aid to the opposition Syrian National Coalition to help it deliver basic governance and other services in rebel-controlled areas.
He also promised direct support in the form of food and medical supplies to rebel forces, in what correspondents say was a shift in US policy on Syria.
Source: BBC News
