Reuters reports: Despite some military defections, Syrian President Bashar al-Assad’s inner circle remains cohesive and the 16-month conflict with rebels is likely to be a drawn-out struggle, senior U.S. intelligence officials said on Tuesday.

That assessment appears to dash any U.S. hopes that Assad, whose ouster Washington has called for, will fall soon of his own accord. The Obama administration has declined to intervene militarily in Syria, citing the lack of international backing and the country’s sectarian divisions.

White House spokesman Jay Carney said on Tuesday that Assad “has been slowly, too slowly, losing his grip over his country. The process, because of his refusal to step aside, has been horrific and has exacted a terrible toll on the Syrian people.”

But U.S. intelligence agencies, watching closely for cracks in Assad’s inner circle, do not see them so far.

“The regime inner circle and those at the next level still seem to be holding fairly firm in support of the regime and Assad,” one intelligence official said on condition of anonymity.

Assad said on Tuesday that Syria was in a “state of war” and snubbed those calling for him to step aside, saying the West “takes and never gives and this has been proven at every stage.

Despite the deterioration in Syria, so far there has been no sign of an appetite for Western intervention like that by NATO against Libya’s Muammar Gaddafi last year. On Tuesday, the Western alliance called the shooting-down of a Turkish warplane by Syrian forces last week “unacceptable” but stopped short of threatening retaliation.

The Independent reports: Some of the fiercest fighting seen since the start of the conflict in Syria raged on the outskirts of Damascus yesterday as better trained and equipped rebels attacked elite forces loyal to the regime.

The increase in violence came as Turkey’s Prime Minister, Recep Tayyip Erdogan, warned that he would order his troops to attack Syrian army units if they dared to approach the countries’ 550-mile shared border.

“Turkey is not a kind of country whose borders and hostility can be tested,” Mr Erdogan told his parliament in Ankara. The threat came after Syria admitted shooting down a Turkish F-4 Phantom jet last Friday, which Turkey claimed was in international airspace after briefly violating Syrian territory.

Describing the Syrian regime as presenting a “clear and present” threat to Turkish security, Mr Erdogan announced a change in the rules of engagement for the country’s military.

Any Syrian military offensive that approached the country’s borders would be considered a legitimate target. Claiming that Syrian helicopters had recently violated Turkish airspace, he said that any future infringement would be met with military action.