The Chinese frigate Changchun during a visit last month to Bandar Abbas in Iran. (Fars)

Last month, visitors to Bandar Abbas on Iran’s southern coast gathered to witness a never-seen-before event: two Chinese warships pulling into port.

It could be just the start of a budding naval alliance stretching from the Pacific to the Persian Gulf.

Iranian and Chinese commanders last week announced plans for greater maritime cooperation. While the details are vague, it clearly touches ambitions on both sides: Expanding the reach of their warships into faraway seas and new ports of call. And, at the same time, giving a jab at the United States and its preeminent naval power.

For China, the Iranian naval alliance offers a convenient way-station for Beijing’s widening outreach in Africa, and another bonding moment in the largely transactional ties between China and Iran. China needs Iran’s oil and gas, and Iran is happy to oblige to help offset Western-led sanctions over Tehran’s nuclear program.

A deepening Chinese-Iranian naval partnership also could be an extra win for Tehran. Iran often boasts about plans to modernize its fleet, but it remains limited to several diesel-electric submarines and a handful of frigate-class vessels, according to the U.S. Naval Institute. Chinese expertise could help fast-track some of Iran's goals, including integration of surveillance and attack drones onto its warships.

But no one is really talking about what could come. Few specifics emerged after Thursday’s meeting in Beijing between the chief of Iran’s navy, Rear Adm. Habibollah Sayyari, and his Chinese counterpart, Adm. Wu Shengli. Agreements were made to “further pragmatic cooperation and strengthen military-to-military ties,” China’s state-run Xinhua news agency reported without elaboration.

Both Iran and China have made it clear they seek to expand their so-called “blue water” navies – capable of long-range voyages in the open sea. The motives, however, are somewhat different. China is a rising naval power and hopes one day to muscle out the U.S. Navy presence in Asia. Iran seeks to use its much more modest navy to remind Washington its influence does not extend into international waters.

Last year, an Iranian destroyer and helicopter carrier docked at the Chinese port city of Zhangjiagang – near Shanghai – after a 40-day voyage. In early 2011, two Iranian navy vessels passed through the Suez Canal and into the Mediterranean for the first time since the 1979 Islamic Revolution, raising alarm from arch-foe Israel.

The navy chief Sayyari has repeatedly pledged that Iranian warships will sail into the Atlantic to shadow the U.S. East Coast just outside American territorial waters. The threat is considered little more than bluster at the moment. But the point is made: If the U.S. Navy can maintain its 5th Fleet base in Bahrain – just across the Gulf from Iranian shores – then America shouldn’t be surprised to see Iranian ships near its coast someday.

“In the same way that the ‘world arrogance’ is present near our sea borders, we will have a powerful presence near the U.S. sea borders,” Sayyari said in 2011, using one of Iran’s mocking phrases to describe the United States.

Sayyari further promised that Iran was developing the naval capabilities to plant its flag on both poles. That day is still well beyond Iran’s reach. Most of its naval forces are designed to stay much closer to home: smaller craft patrolling the Gulf and the Strait of Hormuz at its mouth, the route for one-sixth of the world’s oil supply.

Still, Iran is ambitious. It has sent warships off the coast of Somalia to confront piracy, conducting their own patrols rather than work with an international coalition led by U.S. ships from the 5th Fleet.

“The totality of evidence indicates that Iranian maritime activity in support of the Iranian strategic objective of regional power and influence is evolving and expanding, not contracting,’’ said a June 2013 report by the Institute for the Study of War.

The two Chinese warships that docked last month in Iran – the destroyer Changchun and frigate Changzhou – were also returning from patrols in the Gulf of Aden and off Somalia to protect shipping lanes.

These are increasingly familiar waters for China, whose investments in Africa have risen steadily in tune with Beijing’s long-range policymaking. Beijing views Africa as fertile ground to cultivate reliable allies that will side with China on its key international agendas, such as opposition to Taiwan and various territorial claims. In the latest bid at boosting military ties, China last week began monthlong naval exercises with Tanzania in the Indian Ocean.

But China’s main “blue water” push is in the Pacific, where many Western military analysts believe Beijing’s goal is to one day force out U.S. bases. Last year, a member of China’s National Defense University acknowledged as much. Col. Lui Mingfu was quoted by Australian media as saying China wanted to push U.S. military interests to “east of the Pacific midline” and safeguard the western half for regional powers.

China and the United States have had some brushes in the Pacific, most recently in August, when a Chinese J-11 fighter buzzed a U.S. Navy P-8 Poseidon surveillance plane in the South China Sea – where China and other Asian nations hold competing territorial claims to several islands.

Mostly, however, the Chinese navy has been a spectator sport for the West and allies: Watching a construction boom that has brought the number of Chinese ships and submarines roughly on par to the U.S. strength in the region. The difference, many analysts say, are shortcomings in technology such as advanced sonar and other anti-submarine capabilities.

China wants to close those gaps. Its second aircraft carrier is under construction, estimated to be completed by 2018, according to state media. There's still a long way to go. The United States has 10 active carriers around the world.