Months after the Solomon Islands struck a security pact with China, its leader has repeatedly appeared to snub the United States, heightening Washington's concern but not deterring it from trying to keep the Pacific nation out of Beijing's orbit.

Prime Minister Manasseh Sogavare's unpredictable diplomacy will make it hard for the United States to make up lost ground with the pivotal island nation as China seeks to expand its security presence, former diplomats and other analysts say.

As part of a push to boost engagement and counter China's growing influence, the administration of U.S. President Joe Biden plans to open an embassy for the first time in three decades in the Solomon Islands, an archipelago that switched diplomatic recognition from Taiwan to Beijing in 2019 and in April sealed the security agreement with China.