A report by a US-based international think-tank says Washington should be prepared to spend more money to modernise its military bases on Guam and elsewhere in the Pacific, citing growing tension in Asia.
The report, by the Center for Strategic and International Studies' Asia Programme, says the US is likely to see another series of nuclear and ballistic missile tests with greater technological capability.
North Korea has specifically mentioned Guam -- a US territory -- in past threats towards the US, prompting the Pentagon to station a land-based missile defence system on the island.
The report also calls for clearer policy when it comes to China's growing military and economic power, saying that Washington needs to strengthen ties with South Korea and Japan to provide the best environment in which to welcome China as a rule-abiding power.
The administration of President Barack Obama has overseen a pivot of US military strength towards the Asia-Pacific region, including relocating about 5,000 troops to Guam.
Guam hosts both an Air Force and Navy base, which the report says should be modernised.