The U.S. military is getting an unwelcome reputation: a pushover.

An escalating series of confrontations on the seas and in the skies around the world is creating the perception that the U.S. is the child who's bullied in school because he doesn't fight back.

Whether it's Iran playing chicken with U.S. patrol boats in the Persian Gulf, Russia buzzing U.S. ships in the Black Sea, or China demanding American ships adhere to phony claims of sovereignty over the air and water of the South China Sea, the narrative seems to follow an all-too-familiar script.

The Pentagon denounces the provocations as "unprofessional," issues a stern warning, and then there are no consequences.

"It's like a mom in a grocery store, or a parent, and the kids are running amok and they say 'stop that right now or else,' but the 'or else' never comes, so the kids behave as badly as they want to," said Dakota Wood, a senior research fellow at the Heritage Foundation.

"If there aren't any consequences, then the bad behavior just escalates."

The latest incident occurred Saturday, when a U.S. EP-3 reconnaissance plane, flying off the coast of Iran in the northern Persian Gulf, received a radio threat from the Iranian military.

"Leave the area, or we will shoot you down with missiles," is how one Pentagon official described the menacing communication. The U.S. spy plane ignored the warning since it was clearly flying in international airspace, the official told the Washington Examiner.

Still, emboldened by a lack of concrete response from the U.S., the number and seriousness of such incidents continues to rise dramatically.

So far this year, fast boats from the Islamic Revolutionary Guard Corps Navy have harassed U.S. naval vessels in the Persian Gulf at least 30 times, up 50 percent over last year, according to one unofficial tally.

"This is clearly a pattern, and one we're not happy about," said Pentagon spokesman Navy Capt. Jeff Davis.

But pressed for what the U.S. Navy plans to do change the dynamic, Davis could only say, "I don't have a good answer for you … At this point I can only tell you we are calling upon them not to do this. This is something that presents risk, and it's unnecessary."

It's that kind of noncommittal reply that fuels the kind of frustration voiced by Donald Trump last week when, at a rally in Pensacola, Fla., he said, "With Iran, when they circle our beautiful destroyers with their little boats, and they make gestures at our people that they shouldn't be allowed to make, they will be shot out of the water."

That may sound bellicose, but U.S. ships sailing in international waters and U.S. planes flying in international airspace have not a just right, but an obligation, to defend themselves.

In April, when two Russian fighter jets flew within 30 feet of the destroyer USS Donald Cook, Secretary of State John Kerry warned that "under the rules of engagement, that could have been a shoot-down, so people need to understand that this is serious business."

Another stern warning, followed by another stern warning.

Wood argues the U.S. needs to inform Iran that there are clear limits to how close Iranian vessels can come to U.S. warships, and then take action if Iran doesn't give the U.S. wide berth.

The alternative, argues Wood, is to just put up with harassment. "You could view that as just a bunch of flies buzzing around and they are never really going to do anything, it doesn't really pose a lethal threat."

But that could jeopardize the safety for the ship and its crew. In 2000, the USS Cole was attacked in Yemen by a small boat that pulled up alongside the American ship in the port of Aden showing no obvious hostile intent.

"What if we have an incident like that?" asked Wood. "Then the criticism is going to be how in the world did we allow an Iranian speedboat to get right up next to a United States ship of war."

But blowing Iranian speedboats out of the water is too simplistic an answer, said former NATO Supreme Allied Commander Adm. James Stavridis, who is now an adviser to Hillary Clinton on national security issues.

"We already have the right rules of engagement to deal with both hostile acts and hostile intent," said Stavridis, who advocates a three-track approach that begins with diplomatic warnings and includes more aggressive use of warning shots, flares and electronic jamming with the aim of getting Iran to create a system to resolve incidents at sea, similar to existing agreements the U.S. has with Russia and China.

The need for a system to resolve disputes with Iran was echoed this week by Chief of Naval Operations Adm. John Richardson.

Speaking Monday at a seminar at the Center for American Progress, a Washington think tank, Richardson said, "Getting some kind of a rule set like that ... with the Iranians, would also be helpful, so that we can have these frameworks for behavior that would guide us more to the useful types of encounters at sea, rather than these 'close aboard' types of demonstrations that really don't have any positive benefit."

The top U.S. commander for the Persian Gulf region, Gen. Joseph Votel, said he proud of the way U.S. commanders and crews have exercised restraint and deescalated confrontations that could easily have resulted in deaths.

"In every case that I've seen, they have made very, very good decisions," Votel said at a Pentagon briefing last month. "But ultimately if [the Iranians] continue to test us, we're going to respond and we're going to protect ourselves and our partners."

But other critics suggest that U.S. naval commanders have been cowed by the Obama administration's well-known desire to improve relations with Iran.

Navy Cmdr. Jeremy Vaughan, in an analysis of U.S. naval posture in the Persian Gulf published by the Washington Institute, cited this quote from the official investigation of the capture of 10 U.S. sailors whose riverine patrol boats inadvertently strayed into Iranian waters in January.

"Ok, what's the commander's intent here, the highest commander's intent, the Commander in Chief would not want me to start a war over a mistake, over a misunderstanding," the report quoted the riverine boat commander as saying.

Vaughan, a veteran of several deployments to the Gulf, concludes the commander had the ability and means to escape yet failed to do so, violating the U.S. Navy regulation to repel any search of his vessel.

Votel, the Central Command chief, says he believes the aggressive Iranian actions are driven by "rogue commanders" in Iran's Quds force, the most radical elements of its military, and allowing U.S. ships to be goaded into firing shots in anger could just play into their hands.

Still, Votel warns the confrontations cannot continue indefinitely, "Because ultimately we will prevail here and I'm very, very confident of that and we certainly don't want that to come to pass."