Brussels (dpa) - The European Union could ratchet up its pressure on Thailand to tackle illegal fishing, it warned Thursday, adding that "serious concerns" remain about the country‘s willingness to cooperate.The EU has been cracking down on illegal, unreported and unregulated (IUU) fishing with the threat of import restrictions. It has already banned fish caught by vessels from Cambodia and Guinea due to those countries‘ failure to reform their fishing sectors.Sri Lanka was also on the EU‘s fishing blacklist, but the ban was lifted Thursday, with EU Fisheries Commissioner Karmenu Vella noting that the country now has a "robust legal and policy framework to fight illegal fishing."Thailand, which is the world‘s third-largest seafood supplier, was warned a year ago that it must do more to crack down on illegal fishing practices or else face EU sanctions.The decision, issued by means of a so-called yellow card, threw Thailand‘s fishing industry into disarray and prompted fishermen to go on strike against what they said were unfair government measures to stop illegal fishing.The European Commission is currently "evaluating progress," it said Thursday, noting that a meeting with the Thai authorities is due to take place next month."The dialogue is proving difficult and there remain serious concerns about the steps taken by Thailand to fight IUU fishing activities," the EU‘s executive wrote in a statement, adding that "further action ... cannot be ruled out."Thailand‘s fisheries industry has an inadequate legal framework with ineffective sanctions that fail to deter, poor monitoring systems, and problematic management, the commission said.It also warned about human trafficking and slave labour in the Thai fisheries sector, although these issues are not covered by EU rules on illegal fishing activities.The commission also issued yellow cards Thursday against the Pacific island state of Kiribati, Sierra Leone on Africa‘s Atlantic coast and the Caribbean islands of Trinidad and Tobago.It expressed concern about Kiribati‘s ability to control foreign fishing fleets and said illegally caught fish could be "laundered" through its ports, while listing similar preoccupations about a lack of oversight by the other two states.At least 15 per cent of world fish catches are thought to be illegal, unreported or unregulated, accounting annually for up to 26 million tons of fish worth around 10 billion euros (11.3 billion dollars), according to the commission.EU warnings over illegal fishing are also active against the Comoros, Curacao, Saint Kitts and Nevis, Saint Vincent and the Grenadines, the Solomon Islands, Taiwan and Tuvalu.