Related Rule
United States of America
Practice relating to Rule 66. Non-Hostile Contacts between the Parties to the Conflict
Section B. Use of the white flag of truce
The US Field Manual (1956) notes:
In the past, the normal means of initiating negotiations between belligerents has been the display of a white flag …
The white flag, when used by troops, indicates a desire to communicate with the enemy. The hoisting of a white flag has no other signification in international law. It may indicate that the party hoisting it desires to open communication with a view to an armistice or a surrender. If hoisted in action by an individual soldier or a small party, it may signify merely the surrender of that soldier or party. It is essential, therefore, to determine with reasonable certainty that the flag is shown by actual authority of the enemy commander before basing important action upon that assumption. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 458.
The US Air Force Pamphlet (1976) states:
The white flag has traditionally indicated a desire to communicate with the enemy and may indicate more particularly, depending upon the situation, a willingness to surrender. It raises expectations that the particular struggle is at an end or close to an end since the only proper use of the flag of truce or white flag is to communicate to the enemy a desire to negotiate. 
United States, Air Force Pamphlet 110-31, International Law – The Conduct of Armed Conflict and Air Operations, US Department of the Air Force, 1976, § 8-6a.
The US Naval Handbook (1995) states: “Customary international law recognizes the white flag as symbolizing a request to cease-fire, negotiate, or surrender.” 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-2.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Transportation, US Coast Guard, October 1995 (formerly NWP 9 (Rev. A)/FMFM 1-10, October 1989), § 11.9.5.
The US Naval Handbook (2007) states: “Customary international law recognizes the white flag as symbolizing a request to cease-fire, negotiate, or surrender.” 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 8.5.1.5.
The Handbook also states: “Once an enemy warship has clearly indicated a readiness to surrender, such as by … hoisting a white flag … the attack must be discontinued.” 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 8.6.1.