Al-Qaeda's affiliate in Syria has been ordered by the jihadist network not to use the country to launch attacks on the West, the group's leader has said.
In an interview with Al Jazeera, Abu Mohammed al-Julani said al-Nusra Front was focused on capturing Damascus and toppling President Bashar al-Assad.
He also promised to protect Syrian minorities that disavowed Mr Assad.
A rebel alliance including al-Nusra has been making gains in north-western Syria, capturing the city of Idlib.
Rebel fighters are now advancing on the Mediterranean coastal province of Latakia, a stronghold of the president and his heterodox Shia Muslim Alawite sect.
The hour-long interview with Julani broadcast on Wednesday night was his second with Qatar-based Al Jazeera since 2013, when al-Nusra Front split from what is now Islamic State (IS).
It was not clear where it was filmed and Julani's face was not shown. He sat on an ornate chair opposite the interviewer, Ahmed Mansour, with his back to the camera.
Julani said al-Nusra had been instructed by the overall leader of al-Qaeda, Ayman al-Zawahiri, to avoiding launching attacks abroad that might jeopardise its operations in Syria.
"We are only here to accomplish one mission, to fight the regime and its agents on the ground, including Hezbollah and others," he stressed, referring to the Lebanese Shia Islamist movement that is fighting alongside government forces.
"Al-Nusra Front doesn't have any plans or directives to target the West. We received clear orders not to use Syria as a launching pad to attack the US or Europe in order to not sabotage the true mission against the regime. Maybe al-Qaeda does that, but not here in Syria."
The al-Nusra leader also denied claims by the US that it had a secret cell called the "Khorasan Group" that was tasked with plotting attacks outside Syria.
"There is nothing called Khorasan group. The Americans came up with it to deceive the public. They claim that this secret group was set up to target the Americans but this is not right."
The US-led coalition against Islamic State, to which al-Nusra is violently opposed, has bombed several bases that US officials say were used by the Khorasan group.
"Our options are open when it comes to targeting the Americans if they will continue their attacks against us in Syria. Everyone has the right to defend themselves," Julani warned.
A US intelligence official told the New York Times that Julani's claims were "self-serving propaganda".
Julani also vowed that al-Nusra would not harm members of Syria's Christian and Druze minorities who did not fight against it, and that Alawites would be safe if they "drop their weapons, disavow Assad, do not send their men to fight for him and return to Islam".
"The battle does not end in Qardaha, the Alawite village and the birthplace of the Assad clan," he explained. "Our war is not a matter of revenge against the Alawites despite the fact that in Islam, they are considered to be heretics."