China and Croatia vowed over the weekend to strengthen economic and political ties as the two countries marked 20 years of diplomatic relations.

Croatian President Ivo Josipovic and Chinese counterpart Hu Jintao exchanged messages of congratulations Sunday on two decades of friendly international ties, which have included an ambition by Zagreb to serve as China's gateway to Eastern Europe.

The renewed commitment to stronger relations comes as Chinese shipping group COSCO is considering a $5 billion investment in the Croatian port of Rijeka with the aim of turning it into China's transport link to Europe -- its biggest trading partner.

In the weekend messages, Josipovic said Croatia was "a reliable friend for China in southeastern Europe" and predicted Beijing "would have one more partner and ally in the European Union" after Croatia's entry into the regional bloc in 2013, the state-owned Chinese news service Xinhua reported.

The Croatian leader said he hoped "Croatia and China would continue to advance their cooperation and further cement their friendship," which was officially launched May 13, 1992.

Hu said two decades of diplomacy between the countries had seen the development of "high-level exchanges, deepened political trust (and) expanded cooperation in economy and trade," while reaping "bumper harvests in cooperation in areas such as culture, education and tourism."

A big part of the two countries' relationship has been China's steadfast support for Croatia's accession to the European Union, which Beijing says will play a prominent role in promoting China-EU relations.

"I believe by joining the European Union, Croatia will create new opportunities for growth not only for Croatia but also other countries in the region while opening new space to cultivate the relations between China and the southeastern European nations," Hu said during a 2009 trip to Zagreb.

Already a popular destination for Chinese tourists, Croatia could also soon have thousands of Chinese workers in the country should COSCO follow through on its interest in the Adriatic port of Rijeka.

A Chinese labor force of up to 20,000 workers would be stationed there under plans discussed last month by top COSCO executives and Croatian Prime Minister Zoran Milanovic, multiple local reports indicated.

Milanovic said the details of a Chinese investment in Rijeka would be addressed in due time and assured residents any stationing of foreign workers would be done in accordance with the country's immigration laws, the Croatia daily Free Dalmatia reported.

"We are talking with the potential partners" about the $5 billion proposal, which would also include the rebuilding of a major railroad line between Rijeka, the capital Zagreb and the Hungarian border, the prime minister told reporters April 26 in Warsaw, when Chinese Prime Minister Wen Jiabao met with leaders of 16 Central and Eastern European countries.

But, he added, "nobody will get these jobs without a public tender that sets clear, transparent and predictable conditions."

"We are a state of law and will soon enter the EU," Milanovic said. "When we talk about any jobs, then the rule is public tender and bids for the concession, like every other business."