Voters in Paraguay will cast their ballots in a presidential election on Sunday that could determine the future of its ties with Taiwan.

Thirteen candidates are running in the election, which is held as the incumbent's five-year term is due to expire.

Opinion polls suggest a close two-way contest between the right-wing ruling party candidate Santiago Pena, who is a former finance minister, and the centrist opposition coalition candidate Efrain Alegre.

Paraguay is one of 13 countries that has diplomatic ties with Taiwan, and the only remaining one in South America.

One focal point in the presidential race is the country's relations with Taiwan.

Pena supports maintaining ties with Taiwan, while Alegre has hinted at severing the relations and seeking to open diplomatic ties with China to boost exports of agricultural products such as beef and soybeans.

In recent years, a number of Latin American countries have established diplomatic relations with Beijing, including Honduras, which cut ties with Taiwan in March.