TAIPEI, July 9 (Reuters) - Paraguay's president-elect, Santiago Pena, will visit Taiwan this week and meet "great friend" President Tsai Ing-wen, he said on Sunday (Jul 9), shoring up a relationship at a time China is working to entice the island's dwindling allies.

Paraguay is the last South American country with formal relations with Taiwan. The island, claimed by China as its own, has lost support from other Latin American nations in recent years, including Honduras, which this year ended decades of ties in favour of Beijing.

Taiwan now has formal diplomatic relations with only 13 countries, mostly poor and developing nations in Central America, the Caribbean and the Pacific.

China's efforts to win over Taiwan's friends and expand its influence in countries in the US backyard, especially in Latin America, have caused alarm in Washington.

Pena said on his Twitter account he would visit Abu Dhabi, then go to Taiwan to meet Tsai, who he described as a "great friend".

"We are going to develop an intense international agenda in the coming days carrying the message that Paraguay and its people are up for great things," he tweeted.

Pena had pledged during the election campaign to maintain his country's friendship with Taiwan despite pressure from the local agricultural sector, which wants to open up lucrative Chinese markets to soybeans and beef.

Taiwan's foreign ministry said that on the visit Tuesday through Saturday he would also meet Vice President William Lai, who is the ruling Democratic Progressive Party's candidate in January's presidential election, and Economy Minister Wang Mei-hua.

Pena is being accompanied by some members of his incoming team, including his foreign and finance ministers, the ministry said.

He will be in Taiwan for the 66th anniversary of diplomatic ties on Wednesday, the ministry said.

Pena will take office on Aug 15. Diplomatic sources have told Reuters that Lai might attend as Taiwan's representative, likely transiting the United States to meet US officials.