"We are a law-based state and will soon enter the EU. When we talk about such jobs, when we talk about any job, the rule of public tender and invitation applies, for concessions and any other job," he told reporters.
Milanovic was in Warsaw to attend an international meeting of prime ministers, "Poland - Central Europe - China".
On the fringes of the meeting, he met with Chinese PM Wen Jiabao.
Milanovic said theirs was a political meeting and that he and the PM of one of the economic world powers did not talk about details of investing in a lowland railroad and Croatian railways, which he discussed with Chinese business people in Zagreb earlier this week.
"We are talking with the most serious potential partners, Chinese companies, and given their structure, China is an important partner. But nobody in Croatia will enter such deals without a public tender for which we set clear, transparent and predictable terms," Milanovic said, adding that the government would talk with other partners as well.
On Monday, he held talks with representatives of the China Ocean Shipping Company (COSCO) who are interested in projects that would turn Croatia into a logistics hub and transport corridor for Chinese goods en route to Europe. There was also talk about concrete infrastructure projects such as the reconstruction of the existing railway line between Zagreb and Rijeka and the construction of a lowland railway from Rijeka via Zagreb and Koprivnica to Botovo on the border with Hungary on concession models.
Asked about the truth of media reports that it was an investment of US$ 5 billion and that the Chinese were making it conditional on bringing 20,000 of their workers to Croatia, Milanovic said he and Wen did not discuss technical details that would be dealt with later.
"Regarding work permits for foreign workers in Croatia, the rules are clear and there are no exceptions," said Milanovic.
He also met with Slovenian PM Janez Jansa and announced that they would most probably meet in Slovenia next month, when Milanovic, Croatian President Ivo Josipovic and Parliament Speaker Boris Sprem will visit the mass grave at Tezno in which members of the former Yugoslav army are estimated to have buried at least 15,000 prisoners of war, mainly Croats, whom they killed at the end of World War Two.