The European Commission says Serbia is not ready to start accession talks with the EU because of its tensions with Kosovo, and has criticized Turkey for its human rights record and insufficient reforms.
In its annual report on countries lining up to join the EU, the EU executive said Belgrade also had to make more effort to reform its justice system and protect the independence of its central bank.
Belgrade won the status of EU candidate in March but needs the commission's green light to start actual talks, in a process likely to take years.
The commission said it was increasingly worried over reforms in EU-candidate Turkey.
It listed the rights to liberty and security and to a fair trial, as well as the freedom of expression, as areas of particular concern.
In related news, NATO chief Anders Fogh Rasmussen said the alliance may bolster its peacekeeping force in northern Kosovo, where the Serbian minority rejects the authority of the ethnic Albanian-dominated government.
Speaking after a NATO meeting in Brussels, Rasmussen said that overall troop numbers would remain constant.
"As you know, we have the ambition to gradually reduce our troop presence in Kosovo as the security situation hopefully continues to improve, but because of the volatile situation we have witnessed during the recent 12 months we have postponed the decision to reduce the number of troops in Kosovo," he said.
The comments are important since NATO has been under pressure to reduce its 6,100-strong force, which includes 750 Americans.
Based on Reuters and AP reporting