Six months after Washington and Beijing agreed not to conduct cyber attacks on each other's private sector for commercial gain, a top US spy questioned Tuesday whether China has cut such activities.

In September 2015, President Barack Obama and his Chinese counterpart Xi Jinping announced an accord under which neither the United States nor the Chinese government would conduct cyber-enabled theft of intellectual property.

But Admiral Michael Rogers, who heads the US military's Cyber Command, told lawmakers it was unclear if the Chinese government was holding up its end of the deal.

"We continue to see them engaged in activity directed against US companies. The question I think we still need to ask is, is that activity then in turn shared with the Chinese private industry?" Rogers told the Senate Armed Services Committee in Washington.

He acknowledged nations -- including the United States -- routinely use cyber to "gain access or knowledge" but suggested American spy agencies don't share insights with the private sector.

"The ... issue we've always had with the Chinese is while we understand we do that for nations to generate insight, using that then to generate economic advantage is not something that is acceptable to the US," he said, later adding the "jury is still out" on whether China indeed passes intel to the business world.

The US Cyber Command is charged with protecting America's military and some of its major civilian networks from attacks, as well as deploying its own offensive cyber strategies if needed.

By 2018, it will have more than 6,000 military and civilian technical experts working across 133 teams, Rogers said.

One such team, comprising about 65 people, today works in the Middle East and carries out cyber operations against the Islamic State group's networks.

"USCYBERCOM is executing orders to make it more difficult for ISIL to plan or conduct attacks against the US or our allies from their bases in Iraq and Syria to keep our service men and women safer as they conduct kinetic operations to degrade, dismantle, and ultimately destroy ISIL," Rogers told lawmakers, using an IS acronym.

The Pentagon pans to spend a total of $6.7 billion in the 2017 budget -- up 15.5 percent from the previous year. In all, the Pentagon is projected to spend $34.6 billion over the coming five years.