WASHINGTON — President Donald Trump's desire to prevent future chemical attacks in Syria has fueled speculation that the U.S. leader may authorize an attack that is more far-reaching than the one he launched a year ago.

A larger strike, possibly including stealth aircraft and strikes on multiple sites, could inflict lasting damage to military facilities and economic infrastructure that have been vital to President Bashar Assad's ability to regain his grip on Syria seven years into a grinding war.

But a wider attack will face multiple immediate and longer-term risks, including the possibility of a dangerous escalation with Russia, Assad's main military backer, in a country that Moscow has used as a testing ground for some of its most sophisticated weaponry.

Military officials have declined to comment on the composition or timing of a potential strike on Syria, even as Trump has telegraphed his intentions to take action in response to a reported chemical attack that killed at least 45 people outside of Damascus this month.

"Get ready Russia, because they will be coming, nice and new and 'smart!' " Trump tweeted Wednesday, referring to U.S. missiles.

The Assad regime's suspected use of chemical munitions against civilians galvanized the president to set aside his concerns about involvement in the conflict, just as a reported sarin attack did a year ago, prompting Trump to order a cruise missile strike on an isolated airfield linked to the civilian deaths.

Looming over the military planning are questions about how effective a punitive strike - no matter how broad — will be in deterring Assad from resuming chemical attacks.

Critics assailed Trump for the limited nature of the 2017 attack, which did little to disrupt Syrian air operations or deter the use of chemical weapons, reported repeatedly in the following months.

When President Barack Obama failed to authorize strikes against Syria in 2013 to enforce his "red line" on chemical weapons use, he also sent a message of permission, critics have said, even if that incident resulted in a disarmament deal.

Some analysts say that for the doctrine to work, the country or person the American military is trying to deter must understand what actions will prompt a response from the United States. The U.S. military has responded at times to Assad's use of chemical weapons but at other times hasn't responded at all.

"There have been 20-plus incidents of chemical weapons use," said Rebecca Hersman, a former top Pentagon official now at the Center for Strategic and International Studies. "We have to find a way to respond proportionally, but we have to respond every time, not just when it gets the world's attention."

The response may not be military, but it should extract some sort of cost — whether political, military or economic — each time, Hersman said.

The inconsistent responses from outside powers may have signaled to Assad that he can continue to use the munitions, so long as he uses them in small amounts without causing mass casualties or generating gruesome imagery.

Since last year's strike, multiple chemical attacks have been reported in opposition areas, most of them involving chlorine rather than the nerve agent sarin, suggesting the government may have adjusted its tactics.

"It not only undercuts deterrence theory, it also sends a signal globally that you can use chemical weapons — just don't let them upset us," said Nicholas Heras, a fellow at the Center for a New American Security in Washington. "Why is it that this particular Douma attack was the straw that broke the camel's back for President Trump? It's the images."

Some analysts say the chemical attacks will continue unless Russian and Iran suffer consequences for supporting Assad's tactics.

Among the chief factors military planners must consider are air defenses in Syria, which were bolstered by Russia's decision to enter the war in 2015 and could pose a threat should the Pentagon employ manned aircraft in the attack. Their reach was demonstrated in February when an Israeli F-16 fighter jet crashed amid Syrian antiaircraft fire.

The United States has flown an array of aircraft over Syria since it began strikes against the Islamic State in 2014, but those operations have mostly steered clear of government and Russian activities. The Assad regime has not authorized the U.S. operations, but it also has not tried to shoot down American aircraft.

The S-400 long-range surface-to-air missile system provided by Russia is the most advanced element of an air defense arrangement that also includes older S-300 systems and shorter-range SA-21 and SA-22.

The more capable defenses are arrayed to protect Russian military assets, centered at the Hmeimim air base in northwest Syria, rather than Syrian military facilities across the country. The Assad government has at least 15 air bases in Syria.

"There are definitely chinks in the armor of Assad's air defenses," Heras said. "The key question is: In western Syria, where the bulk of the high-value targets are, does the U.S. risk more than cruise-missile strikes?"

If the United States opts for a broader attack, it may choose to conduct initial precision strikes to debilitate ground air defenses. It might also decide to combine missiles and stealth aircraft, such as the F-22 fighter jet or B2 bomber, said David Deptula, a retired Air Force lieutenant general who is dean of the Mitchell Institute for Aerospace Studies.

A broader attack could also target command and control nodes, munitions storage sites, or Assad's helicopter fleet, which has been used to deliver barrel bombs and other munitions. The Pentagon might also take aim at civilian airports, seaports, chemical factories or refineries, all of which are vital to Syria's already battered economy.

"You want to destroy the vital infrastructure," Deptula said. "That's the whole point of a punitive attack."

Military officials must consider the response from Russia, which has threatened to conduct counter-strikes against the United States and has positioned some of its most advanced weaponry, including the stealth SU-57 fighter, in Syria.

No matter what the president authorizes, it will be difficult for Washington to enforce battlefield norms in Syria when Trump has called for disengaging from the conflict. The White House has stopped calling for Assad's ouster, while the U.S. military is racing to defeat remnants of the Islamic State before it is required to withdraw the 2,000 U.S. troops there.

