U.S. to China: Let's talk about your nukes

China is modernizing its military at a "remarkable rate," including its own nuclear weapons capability, says a congressionally mandated panel exploring the relationship between the United States and China.

In its annual report to Congress, the U.S.-China Economic and Security Review Commission said China has spent the past two decades improving and advancing its military nuclear posture and could have a "triad" of land, sea and air delivery systems "within the next two years."

China's People's Liberation Army "reportedly tested a variety of new nuclear ballistic systems in 2012, including a submarine-launched intercontinental ballistic missile," Dennis Shea, chairman of the commission, told reporters Wednesday.

"We just urge Congress to get a better handle on the size of the Chinese nuclear arsenal, as well as the nuclear doctrine of China."

Estimates vary as to the exact size of China's nuclear arsenal, but most Western assessments, including those of the United States, say China possesses somewhere between 100 to 500 weapons. Members of the commission said the United States should push for more transparency and understanding from the Chinese on the size of their arsenal.

"We just don't know," Larry Wortzel, another member of the 12-person panel told reporters. "The Department of Defense seems especially stubborn about not changing its estimates."

And China's absence from the types of nuclear-arms reduction and limitation treaties the United States has with countries like Russia is another area ripe for action, the commission said.

"If the Chinese are going to go forward with all these modernization efforts which they are undertaking -- road, mobile and air -- they are going to upend the entire arms control regime that currently exists," C. Richard D'Amato, another commissioner on the panel, said.

"They need to be brought into some sort of dialog to develop some kind of understanding as to where we are all going together on arms control."

In addition to its nuclear arsenal, China has had a busy year modernizing other parts of its military machine, the report said.

Apart from commissioning its first aircraft carrier, China test flew a second advanced fighter with potential stealth capabilities, improved on its satellite navigation system, and expanded the scope of its military exercises and training activities.

The report sent to Congress on Wednesday also covered areas in U.S.-Chinese trade and economic capabilities, China's role in cyberespionage, and the consequences of its demand and consumption of global resources.