Washington (CNN) The senior US military commander in the Middle East said Tuesday that he is "very focused" on Iran's activities in the Persian Gulf after a series of tense encounters between US and Iranian military vessels.

"In recent months, we've seen an uptick in confrontations by Iranian vessels in the Arabian Gulf," Gen. Joseph Votel, commander of US Central Command, said at a Pentagon news conference. "In recent days, we have witnessed even more provocative activity," he continued, adding that the behavior was "very concerning."

In a series of near-confrontations, the hardline Iran Revolutionary Guard Corps navy has conducted live rocket fire exercises near US ships, floated surveillance drones over American warships and, just last week, sent boats tearing toward US vessels at dangerously high speed.

But the military provocations are just one of many antagonistic steps Iran has taken against the US in the past few months, a slew of hostile measures driven by several factors, including a desire to put the next US administration on notice that Iran is no pushover and a faction in the Iranian government struggling with the implications of the nuclear curbs it conceded to international powers.

On top of military aggression, Tehran has arrested dual US-Iranian citizens, targeted Iranians associated with the US, excoriated Washington in official speeches and, this week, installed a Russian-made air missile defense system.

Several threads are feeding this dynamic in Iran, including existential concerns, internal political wrangling, the desire to project a defiant image and financial considerations, such as the price of oil, as the deal halting parts of Tehran's nuclear program in exchange for easing sanctions hasn't delivered substantial economic relief.

The deal went into effect in January, easing years of stringent international sanctions on Iran but at the same time prompting Iranian hardliners -- including Supreme Leader Ayatollah Khamenei and the military-security establishment -- to emphasize Iran's opposition to the US.

"The Iranian establishment believes that it has to demonstrate to the United States that it has not agreed to the nuclear deal from a position of weakness lest Washington employs coercive pressure to alter Iran's regional or domestic policies," said Ali Vaez, senior Iran analyst for International Crisis Group.

It's one reason, he added, "why they have ratcheted up their missile tests and have acted in a provocative way in the Persian Gulf waters."

There's also an existential component to the actions of Iran's hardliners, according to analysts. For decades, the Iranian supreme leader and the country's Revolutionary Guard Corps have positioned their country in stark opposition to "the Great Satan" -- the US -- making that central to the regime's identity and purpose.

That premise came under strain during nuclear negotiations when Iran engaged with Washington at length.

Iran's state power "therefore feels that it has to reassure its main constituents that dealing with the 'devil' does not change the devil, or Iran's relations with it, and the system is not on the verge of a slippery slope of compromises that would end in its unraveling," Vaez said.

IRGC Navy Admiral Ali Fadavi emphasized in an August 11 report by the state FARS news agency that his navy "has been on the forefront of the confrontation with the Americans in the past thirty years." He castigated Iranian moderates "who sought entente with the Satan while ignoring the power of the Islamic Revolution."

Votel calculated that "about 90% of these unsafe, unprofessional activities" are by the IRGC navy and not Iran's general navy.

"So this is, in my view, is not about the Iranian people," Votel said. "It's about the Iranian regime and their desire to continue to do these types of things that stoke instability or attempt to stoke instability in the region."

Iran has arrested three US-Iranian citizens in the last few months, a counterpoint to its release of five American prisoners in January.

US businessman Siamak Namazi was arrested in October. In February, Namazi's father went to Iran to see about his son's release and was arrested as well. In July, San Diego resident Reza "Robin" Shahini was arrested while visiting his ailing mother. Four dual nationals visiting Iran from Britain, France and Canada, all close US allies, have also been imprisoned in recent months.

Though the arrests are likely partly due to concerns about growing Western influence in the wake of the deal, frustration over its actual implementation may be driving some of these hardline steps, too. The supreme leader blasted the pact in an August 1 speech in which he said the US had broken promises.

"America is damaging us from behind the scene," Khamenei said, according to his English language website. "It is preventing our country from establishing economic relations with other countries."

He added that "no tangible and palpable effect has been witnessed in the living conditions of the people" following the execution of the agreement.

Indeed, Iranians associated with the nuclear deal have also been targeted. On August 7, Iran announced that it had hanged Shahram Amiri for "revealing secrets to the enemy." A nuclear radiation specialist, Amiri had escaped to the US where he allegedly helped the CIA understand Iran's nuclear program. He returned to Iran in 2010 and then disappeared.

On August 19, the regime arrested an Iranian Canadian close to the team that negotiated the nuclear agreement. News reports said that Abdolrasoul Dorri Esfahani is facing accusations of espionage.

Instability in the Gulf could benefit Iran and the IRGC economically, says analyst Farzin Nadimi, a security and defense analyst who focuses on the Persian Gulf -- another possible reason for recent provocations.

Reviving the conflict with America helps the IRGC justify its substantial annual budget for operational and R&D purposes, Nadimi wrote in a paper for the Washington Institute for Near East Policy. And then there's oil.

Iran sits on one side of the Strait of Hormuz, which connects the Persian Gulf to the Arabian Sea and is considered the world's most important throughway for oil.

Thirty percent of the world's seaborne traded oil goes through the strait; any sign of trouble can send prices higher and benefit Iran, which has tripled its oil exports since late 2015.

Nadimi noted that last week, when four IRGC boats in the Gulf conducted a high-speed intercept of the USS Nitze and a day later, the USS Squall fired off several warning shots at another set of nearby Iranian boats, oil prices rose 1%.

It's a possibility "that the regime hopes to stimulate global oil markets by causing problems in the Gulf," Nadimi wrote.