A pledge by a leading Honduran presidential candidate to embrace China and de-emphasise Taiwan ties if she wins Sunday's election has prompted diplomatic jostling between Beijing and Washington as each seeks to exert influence on the Central American nation.

Honduras, with a population of just under 10 million, is one of a shrinking club concentrated in Central America and the Caribbean that maintains relations with US-backed Taiwan, which China views as a wayward province.

Leftist Honduran presidential hopeful Xiomara Castro, who has sought to consolidate opposition to a dozen years of conservative rule, said in her election manifesto...