A US navy ship, the USS Essex, is on a high profile visit to Hong Kong in a sign that military tensions between China and the US could be relaxing.
Beijing suspended military contact between the two countries in February.
In October a visit by the USS George Washington to Hong Kong was reportedly cancelled; US officials said this was for operational, not political reasons.
Tensions between the two countries have been strained by disputes over trade, currency and territorial claims.
Beijing suspended military ties with the US in February in protest over US arms sales to Taiwan, although recent talks have opened prospects for a return to military-to-military talks.
China has been further angered by US statements backing South East Asian claimants to the South China Sea; US military exercises with South Korea; and US backing for Japanese claims to islands in the East China Sea that China also claims.
China has irked the US by resisting pressure to cut its trade surplus and loosen its control of the yuan, withholding support from US proposals at the recent G20 summit.
The USS Essex, which carries 2,200 sailors and serves as the flagship of the Essex Amphibious Ready Group, is making a four-day port call in Hong Kong.
The BBC's Annemarie Evans in Hong Kong says the US navy usually invites on board local Hong Kong government leaders and representatives of China's military but that did not happen this time.
The USS Nimitz, a huge nuclear-powered aircraft carrier, was allowed to dock in Hong Kong in February.
Such visits were regular and non-controversial when Hong Kong was still a British colony, but China has, on occasion, banned port visits since it took over sovereignty of Hong Kong in 1997.
The USS Kitty Hawk was denied entry in 2007 in what some analysts said was a retaliation after the US Congress awarded its highest civilian honour to the Dalai Lama.
US Defence Secretary Robert Gates has said the US wants a larger military presence in Asia but does not seek to contain China.
Concerns have intensified around the region since China published maps earlier this year claiming the entire South China Sea as part of its territory.