WASHINGTON — The chairman of the US Senate Armed Services Committee said President Barack Obama should take a hard line on China over cyber espionage against the US, and that the ability of a Washington-Beijing cyber accord inked in September to curb hacking is unclear.

Sen. John McCain, in two Nov. 18 letters, said he wants the White House to use tougher tools to combat foreign hackers. He and accused the administration of dawdling on a cyber deterrence strategy and blasted the administration for not taking advantage of its power to sanction China over a spate of recent cyber attacks.

"This administration has so far refused to articulate a robust strategy to deter cyber attacks against the United States," McCain, R-Ariz., said in one of the letters. "Repeated attacks demonstrate the potential cost of a weak cyber strategy and the national security price we must pay for refusal to utilize available tools to deter further cyber attacks."

In letters to Attorney General Loretta Lynch, Homeland Security Secretary Jeh Johnson and Director of National Intelligence James Clapper, McCain highlighted measures in the the 2015 defense policy bills that grant the president new authorities to sanction individuals who benefit from cyber espionage — a potential deterrent against "the further theft of American economic, military, and political secrets," and "a more powerful tool than the symbolic steps this administration has taken to date."

McCain also pointed to an executive order Obama signed April 1 in which the president asserted that he can sanction not only on countries and corporations whose cyber activities threaten national security, but also individuals.

"The theft of economic data means the United States is footing the bill for the research and development of our enemies to acquire tools to be used against us," McCain said. "And this will continue until our adversaries understand that attacking and pilfering the United States in cyberspace is no longer a low-cost endeavor, but instead will carry real consequences, in the form of sanctions or otherwise."

The administration was reportedly preparing an unprecedented package of sanctions against Chinese firms and individuals over cyber espionage, a month ahead of Chinese President Xi Jinping's state visit to Washington. Instead, Obama announced a bilateral commitment with China that neither government would support cyber theft, but "questions remain" about penalties for violating the agreement, McCain said.

A week earlier at a think tank event, a senior Justice Department official — speaking of the September agreement — said the US could consider criminal charges or sanctions against China if it the U.S. determines hackers there are violating an agreement not to conduct economic cyber espionage on American industry, The Associated Press reported.

"It was great we agreed to this norm, but that's all the more reason when we agreed to this norm, why, when people violate that and you catch them, there's a price to pay, be it criminal or through sanctions," John Carlin, the Department of Justice's top national security attorney, said Nov. 10, according to the AP report.

National Security Agency Director Adm. Mike Rogers, who also heads US Cyber Command, did in recent days hint that China might find itself the target of unwelcome cyber intrusions.

"To my Chinese counterparts, I would remind them: Increasingly you are as vulnerable as any other major industrialized nation state. The idea that you can somehow exist outside the broader global cyber challenges I don't think is workable," Rogers said Saturday at the Halifax International Security Forum.

Andrew Clevenger contributed to this report from Halifax, Nova Scotia.

Twitter: @reporterjoe