Syrian President Bashar al-Assad has vowed to "liberate" every inch of the country lost to rebel groups the same way his forces recaptured the historic town of Palmyra from the Islamic State of Iraq and the Levant group (ISIL, also known as ISIS).

In a televised speech on Tuesday before the country's new parliament, Assad told politicians that the situation on the ground was much better than it was months ago and was improving by the day.

"As we liberated [Palmyra] and before it many areas, we will liberate every inch of Syria from their hands. Our only option is victory, otherwise Syria will not continue."

In the speech, Assad also hardened his position on UN-sponsored peace talks, stressing that Syria would be ruled by a "unity government" not a "transitional governing body" as called for by the opposition.

"We will not agree to any topic outside the statement of principles we presented to the UN. We just won't accept it," Assad defiantly told parliament.

Assad's comments were a far cry from remarks he made last July when he conceded that his army was facing a series of setbacks on the battfield and was being forced to relinquish certain areas.

Palmyra is a major turning point in Syria's Civil War

However, the scales of war have tipped in Assad's favour since Russia began an aerial campaign last September, helping the government troops to capture wide areas from rebel groups.

The Syrian army is currently advancing on Raqqa, ISIL's de facto capital, and in March, Syrian forces evicted ISIL from Palmyra.

ISIL, which controls large swaths of territory in Syria and Iraq, is fighting Syrian troops, US-backed fighters and other rebel groups in northern Syria and is facing an offensive by Iraqi government forces and Shia militias on its stronghold of Fallujah.

Syria's war has proved the longest and bloodiest of the conflicts that arose out of popular uprisings in Arab countries over the past two years and led to the downfall of autocratic regimes in Tunisia, Egypt, Libya and Yemen.

The conflict started in March 2011 as a largely unarmed uprising against President Bashar al-Assad, but it quickly evolved into a full-on civil war between government forces and rebel groups.

United Nations Special Envoy to Syria Staffan de Mistura recently estimated that 400,000 people had been killed throughout the five years of violence