Acquired by the United States Navy for service as a collier and supply ship, Nero was part of the first mobile Fleet Train, organized to meet logistic demands created by far-flung U.S.

Sailing by way of Honolulu and Guam, the collier arrived Manila on 14 August and remained there supporting U.S. forces occupying the Philippines until departing on 4 October on a coaling voyage, steaming to Taku, China and Nagasaki, Japan, before returning to Cavite on 20 November.

Nero recommissioned on 10 April and sailed five days later for the Hawaiian Islands for deep sea soundings, then steamed via Guam to the Philippines arriving Cavite on 4 August.

On 9 February 1901, the collier sailed for the United States, taking the long way home by way of Ceylon, Suez, Algiers, Malta, and Gibraltar, and docking at Norfolk on 16 April.

Once again steaming through the Mediterranean, the Suez Canal and the Indian Ocean, the well-traveled collier arrived at Cavite on 21 December, where she remained for one month, giving needed logistic support, and then returned the way she had come, putting into Boston on 28 April 1903.

She remained in the Pacific, making one voyage to Honolulu and then Kiska in the Aleutians from 14 April to 22 August, then departed Mare Island to return around Cape Horn to Norfolk, arriving on 2 March 1905.

On 19 July, she departed San Francisco for New York, to meet the demand for auxiliaries in the Atlantic due to the increasing scope of U.S. naval operations in World War I.

She sailed for Europe via the Azores on 11 September and shortly after her arrival at Queenstown, Ireland on 13 October, was assigned to duty with the newly formed Naval Overseas Transportation Service.

After unloading, the collier proceeded to New York on 22 April, and then cruised the east coast for the next month, carrying cargo to New England and Middle Atlantic ports until arriving Charlestown on 22 May for extensive overhaul.

On 14 August 1920, she sailed to Hampton Roads to load cargo and then steamed to the Caribbean to coal U.S. naval vessels at Guantanamo Bay and Santo Domingo, returning to Norfolk on 28 September.