Premier Li Keqiang has told Greek Prime Minister Alexis Tsipras that China is prepared to boost investment in the debt-ridden country after conflicting messages about the sale of the country's biggest port.

Li telephoned Tsipras to congratulate him on his election victory last month and invited him to visit China, a Greek government official said on condition of anonymity, as the talks were private. Li's offer of more investment came as talks stalled with the European Union on further funding for Greece.

Tsipras came to power on pledges to throw out EU-imposed economic austerity measures and his government has sent mixed signals about whether it will go ahead with sales of state assets, including a 67 percent stake in Piraeus Port near Athens that China Cosco Holding Co. wants to buy. The port would become a key link in the trading route to Europe that China is developing, and which it dubs a modern-day Silk Road.