"Relations between China and Portugal are entering their best period... We must develop existing projects and step up our commercial exchanges," Xi said at a meeting with counterpart Marcelo Rebelo de Sousa.
"Portugal is an important hub in the land and maritime silk routes," Xi said. De Sousa added Sines was "the symbol of a partnership which we want to continue to build."
Andre Verissimo, editor of the leading business newspaper Jornal de Negocios, said: "If Portugal joins the initiative, it will become the first country in western Europe to do so." Portugal, one of western Europe's poorest countries, opened to Chinese investment after being hit hard by the 2008 global financial crisis.
Investment from China accounted for 3.6 per cent of Portugal's GDP between 2010 and 2016, according to figures from Spain's ESADE business school.
But China's growing influence in Europe, welcomed by Greece and some east European countries, is viewed warily by others on the continent.
At the initiative of France and Germany, EU countries last week agreed on a framework regulating foreign investment, particularly from China.
"In Portugal, we are not anxious about the origin of foreign investment," Costa said, asking Europe to eschew "the path of protectionism."
China now owns a 28 per cent stake in Portuguese energy utility EDP, the country's largest firm, via China Three Gorges and China's state-owned international investment company CNIC.
Perhaps the most contentious issue is China Three Gorges' bid to take a controlling stake in EDP, of which it is already the main stakeholder. The operation, launched in May, involves some nine billion euros.
China has risen to Portugal's 11th-largest trade partner in the decade since 2008, when it was 28th on the list.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)