Beijing considers self-ruled Taiwan to be part of its territory and has vowed to seize the island one day.
It does not permit countries to recognise both Beijing and Taipei, and has used economic inducements in recent years to lure away Taiwan's allies.
Xi's remarks during a meeting with Honduran President Xiomara Castro in Beijing came after Tegucigalpa officially opened an embassy in the Chinese capital.
The switch of allegiances marked "a historic decision and demonstrated your firm political will", Xi told Castro, according to state broadcaster CCTV.
"China will unwaveringly develop friendly China-Honduras relations and firmly support the economic and social development of Honduras," Xi was quoted as saying.
He said China would seek to develop ties "from a strategic height and long-term perspective, turning the beautiful vision of cooperation between the two countries into concrete results".
Castro is expected to sign a host of agreements during her visit.
In March, Honduras cut diplomatic ties with Taiwan in favour of Beijing, reducing the number of countries that diplomatically recognise Taipei to just 13.
China opened an embassy in Tegucigalpa last week.
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