UK advised Bulgaria to keep its Kozloduy nuclear power plant (NPP) units shut, UK minister for Europe Geoff Hoon said after meeting Bulgaria's Foreign Minister Ivailo Kalfin in Sofia.

The units' re-opening will counter Bulgaria's EU accession treaty,  Hoon said as quoted by Bulgarian news agency BTA.

Kalfin said that it was important for Bulgaria to implement its EU accession treaty. The country risked to send wrong signals to the EU if it continued seeking re-opening of the units.

Bulgaria had to close units three and four of its six-reactor NPP as a pre-condition for the country's EU accession. The units were shut down on December 31 2006 and ever since Bulgaria seeks ways to restart them.

Possible electricity crisis is among Bulgaria's main arguments, as the country lost its position as the biggest electricity exporter on the Balkans.

Hoon and Kalfin also discussed UK's restrictions on the free access of Bulgarian migrant workers to the local labour market. Hoon said that the restrictions will be reviewed within one year, as promised.