PRAGUE, Aug 22 (Reuters) - The tender for a new bloc at CEZ's Dukovany nuclear power plant could be launched by the end of this year, Industry Minister Karel Havlicek said on Sunday.

State-controlled CEZ should be able to launch the tender - the Czech Republic's largest single investment estimated to be worth at least 6 billion euros ($7 billion) - once bidders have responded to a security questionnaire.

"In my view, it is a matter of maximum one month from the moment the security questionnaires arrive," Havlicek said in a Czech Television talkshow.

Bidders are supposed to submit their responses to the questionnaire, prepared by the interior and industry ministries, by the end of November.

"I can imagine (the tender being launched in December), maybe already in November, if the responses come sooner, because all signalled they have no problem with the questionnaire," he said.

Westinghouse of the United States, France's EDF and South Korea's KHNP are seen as potential bidders to expand the nuclear plant after companies from China and Russia were excluded.

Czech authorities excluded China from the tender in January and dropped Russia in April amid a security row with Moscow over a deadly blast at an arms depot. ($1 = 0.8550 euros) (Reporting by Robert Muller; Editing by David Clarke)