The 30-year-old midfielder has told new Czech Republic boss Michal Bilek to consider their country's next generation of talent after the failure to qualify for the World Cup in South Africa.
'I want to concentrate on the English league,' said Kovac, who scored twice in 30 appearances for his country.
Committed Hammer: Radoslav Kovac in action during West Ham's FA Cup loss to Arsenal
'Now at West Ham we have an ambitious project. 'It has been a long andbeautiful experience. I've played at the World Cup and EuropeanChampionships, winning with the youth team (at the 2002 Under 21European Championship). I'm over 30, so I decided to quit.'
Kovac spent the second half of last season on loan at West Ham, before securing a £2million move from Spartak Moscow in the summer.
He has made 14 league appearances for the Hammers this season, but has found the back of the net on just one occasion.
West Ham boss Zola confident he won't have to sell his top stars this monthWest Ham 1 Arsenal 2: Gunners late show breaks Hammers heartsCredibility gap: West Ham fans stay away as Zola promises to 'have a go'WEST HAM FC