WASHINGTON  A plan to create a new Pentagon cybercommand is raising significant privacy and diplomatic concerns, as the Obama administration moves ahead on efforts to protect the nation from cyberattack and to prepare for possible offensive operations against adversaries’ computer networks.

President Obama has said that the new cyberdefense strategy he unveiled last month will provide protections for personal privacy and civil liberties. But senior Pentagon and military officials say that Mr. Obama’s assurances may be challenging to guarantee in practice, particularly in trying to monitor the thousands of daily attacks on security systems in the United States that have set off a race to develop better cyberweapons.

Much of the new military command’s work is expected to be carried out by the National Security Agency, whose role in intercepting the domestic end of international calls and e-mail messages after the Sept. 11, 2001, attacks, under secret orders issued by the Bush administration, has already generated intense controversy.

There is simply no way, the officials say, to effectively conduct computer operations without entering networks inside the United States, where the military is prohibited from operating, or traveling electronic paths through countries that are not themselves American targets.