The opposition's sharp reaction underlines how those seeking to topple the Syrian leader might be more prepared to tangle with Israel if they came to power.
Wednesday's Israeli airstrike that U.S. officials say hit a convoy of anti-aircraft weapons bound for the militant Lebanese Hezbollah group also has fueled rage among many Syrians who say they now must fear warplanes from both Assad's forces and Israel.
"Assad never once in his life stood up to Israel," said Kamal Labwani, a prominent Syrian dissident and member of the Syrian National Coalition, an umbrella group of those trying to oust Assad. "All he ever did is `reserve the right to retaliate' but he never retaliated against anyone other than the Syrian people and the Free Syrian Army."
Syria's army chief of staff, Gen. Ali Abdullah Ayoub, warned Friday against testing his country's capabilities.
That was a day after Syria's ambassador to Lebanon, Ali Abdul-Karim Ali, said Damascus "has the option and the capacity to surprise in retaliation," but that it was up to the relevant authorities to choose the time and place.
The comments reflected increased tension between Syria and Israel.
Up to now, the Jewish state has refrained from actions that could be interpreted as intervention in Syria's civil war. But the Syrian government's overall response to this week's airstrike was seen as passive, and most Syrians said they did not expect their military to retaliate.
"I am 100 percent sure the regime will not retaliate," Mosab, a rebel fighter told The Associated Press in a telephone interview. The fighter, who was deployed near the Syrian capital, Damascus, declined to give his full name or precise location for security reasons.
The uprising against Assad began in March 2011 with largely peaceful pro-reform protests and developed into a civil war which the United Nations says has killed more than 60,000 people. The Syrian government maintains that there is no uprising in Syria but a conspiracy against the country because of its support for anti-Israeli groups.
Assad and his late father, Hafez, who together have ruled Syria for four decades, have often tried to draw political legitimacy from the country's combative stance toward Israel. The Assad regime has long sheltered radical Palestinian groups and has facilitated Iran's assistance to militant groups Hamas and Hezbollah.
Israel captured the Golan, a strategic plateau, from Syria in the 1967 war, and Syria demands the area back as part of any peace deal. But despite the hostility between the two countries, Israel and Syria have not gone to war since 1973 and Syria has kept the border area largely calm for decades.
In 2003 and again in 2007, Israeli warplanes struck targets in Syria. And in 2006, Israeli jets flew over Assad's palace in a show of force after Syrian-backed militants captured an Israeli soldier in the Gaza Strip.
Syrian vowed to retaliate for the attacks but never did.
On Friday, Syria's opposition coalition criticized the government for not defending the country against the latest Israeli air raid, saying the Syrian army is too busy shelling civilian areas in Syria.
"This is not the first time that Israeli warplanes violated Syrian sovereignty under the eyes and ears of those who are supposed to protect it," the coalition said in its statement. "Israelis have gotten used to condemnations and strong words that turn out to be nothing more than media bubbles."
It is a real tragedy, the statement said, that while the regime's warplanes and helicopters bombed civilian homes in one part of Syria, Israeli jets attacked targets in another.
The opposition group promised the Syrian people it would use political and diplomatic means to halt such attacks and said it would establish a "deterrent force" to guard against any such future attacks.
Those comments raised the question about how those seeking to topple Assad would handle the thorny issue of relations with Israel if they came to power.
Many among Syria's disparate opposition leaders are Syrian and Arab nationalists fiercely opposed to the Jewish State.
Mouaz al-Khatib, a 52-year-old preacher-turned-activist, has been criticized by some for calling Zionism a "cancerous movement" and praising Iraq's late dictator Saddam Hussein for "terrorizing the Jews."
The umbrella group is dominated by members of the fundamentalist Muslim Brotherhood, which is known for its enmity to Israel. And among the overwhelmingly Sunni Muslim rebels who are fighting to end Assad's rule, the Islamic extremists are gaining dominance.
Labwani, the Syrian dissident, told the AP that "unlike Assad, we know who the real enemy is."
"The first thing we would do is ask U.N. peacekeepers on the Golan to leave, and we will free occupied Syrian territory. We want all our rights."
On Friday, Israeli warplanes flew over south Lebanon, part of stepped up flyovers that residents and Lebanese officials say have been under way all week.
Israel had no comment on Lebanon's description of the air force flights over the border region. Israeli planes frequently fly over southern Lebanon, and Lebanon often files complaints with the U.N. over the incursions into its airspace.
According to a U.S. official, the Israeli airstrike Wednesday near Damascus targeted trucks containing SA-17 anti-aircraft missiles. The trucks were next to the research center the Syrians identified, and the strikes hit both the trucks and the facility.
Advanced anti-aircraft missiles like the SA-17 in the hands of Hezbollah could change the strategic equation, which so far has allowed Israel to send warplanes over Lebanon practically unopposed.
The Syrian military denied that the target of the attack was a weapons convoy. It said low-flying Israeli jets crossed into the country over the Israeli-occupied Golan Heights and bombed a scientific research center. The facility is in the area of Jamraya, northwest of Damascus, about 15 kilometers (10 miles) from the Lebanese border.