President Bashar al-Assad said that Syria would respond to any future attacks on its territory by Israel
Syria's President Bashar al-Assad has warned Israel that it will respond in kind to any future air strikes.
In an interview with a Lebanese TV channel, he said there was "popular pressure" to open a military front against Israel in the Golan Heights.
He also suggested Syria may have received the first shipment of an advanced Russian air defence system.
Israel has warned it would regard the Russian missiles as a serious threat to its security.
Mr Assad's comments came as a Syrian doctor in the strategic town of Qusair, the scene of heavy fighting in recent days, described the horrors of living there.
There were more than 600 injured people trapped in rebel-held districts with no access to medical assistance, he told the BBC.
"They are waiting three to four days for drinking water and that doesn't include the water they need for everyday use for washing their clothes and for normal day-to-day activities," he added.
There were women and children "dying in the battle for more control" of the town, which lies 30 km (18 miles) south-west of Homs, he said.
He said he had seen the bodies of "many" fighters from the Lebanese Shia movement Hezbollah and described their participation in the conflict as a game-changer.
Gen Selim Idriss, the military chief of the main umbrella group of Syrian rebels, the Free Syrian Army, told the BBC on Wednesday that more than 7,000 Hezbollah fighters were taking part in attacks on Qusair.
Meanwhile, US and UK officials are looking into unconfirmed reports of an American woman and British man killed in Syria.
This follows a report aired by Syrian state TV showing the corpses and identity cards apparently of Westerners killed by government troops while fighting for the rebels in north-west Idlib province.
The woman's family later reported her death, naming her as Nicole Mansfield, a 33-year-old Muslim convert from the town of Flint, Michigan.
Speaking to al-Manar TV, which has close ties to Hezbollah, a close ally of the Syrian government, Mr Assad warned: "We have informed all the parties who have contacted us that we will respond to any Israeli aggression next time."
"There is clear popular pressure to open a new front of resistance in the Golan," he added.
Israel has occupied the Golan Heights since the 1967 war. It annexed the territory in 1981, in a move that has not been recognised by the international community.
Syrian shells have hit Israeli positions on the Golan Heights, though it is unclear whether they were aimed at rebels in border areas, and Israel has returned fire.
Syria and Israel have been in a state of war since 1948 but the border had been relatively calm in recent years.
Excerpts released from the al-Manar interview ahead of broadcast quoted Mr Assad as saying Syria had already received a first shipment of S-300 missiles from Russia.
But in the interview itself, he said only: "All we have agreed on with Russia will be implemented and some of it has been implemented recently, and we and the Russians continue to implement these contracts."
The S-300 is a highly capable surface-to-air missile system that, as well as targeting aircraft, also has the capacity to engage ballistic missiles.
Ahead of the interview, Israeli government minister Silvan Shalom said Israel would "take actions" to ensure that advanced weapons did not reach groups such as Hezbollah, but there was no need to "provoke an escalation".
He told public radio: "Syria has had strategic weapons for years, but the problem arises when these arms fall into other hands and could be used against us. In that case, we would have to act."
Israel has already carried out three air strikes on Syria to stop the transfer of advanced weapons to Hezbollah in Lebanon.
Talks about talks
Mr Assad also said Syria would "in principle" attend a peace conference backed by the US and Russia, if there were not unacceptable preconditions.
The main opposition group outside Syria said it would not join the talks while massacres continued.
Its interim leader, George Sabra, said talk of diplomatic conferences was farcical while Syrian government forces backed by Hezbollah were carrying out heinous crimes.
The opposition has been meeting for more than a week in Istanbul to elect new leaders and devise a strategy.
For his part, Mr Assad said it would not be surprising if the conference failed, and if it did, it would not make much difference on the ground, because what he called the "terrorism" of the rebels would continue.
Russian, US and UN officials will meet next week in Geneva to prepare for the proposed conference in June.