An end-of-the-decade programming glitch is causing problems for holders of millions of German credit and ATM cards.

Some 20 million ATM cards, known as Girocards or EC cards in Germany, and 3.5 million credit cards are affected, according to a statement Tuesday by the German Savings Banks and Giro Association (DSGV). Officials from DSGV could not be immediately reached.

The problem is related to a programming error with ATM terminals and point-of-sale devices. DSGV said it expected up to 85 percent of the POS terminals to be updated and fixed by Thursday.

Most of the cards were issued by German financial institutions. Those holding German cards who are overseas can try to use their cards, as about half are fine and the other half will work despite the problems with terminals within Germany, DSGV said. But the association did recommend that people keep enough cash on hand just in case the cards don't work.

The fiasco prompted one smart-card vendor to issue a press release saying its cards were not at fault. Oberthur Technologies, a smart-card and ATM technology vendor based in France, said in a statement on Wednesday that its German-issued cards were functioning.

It wasn't clear from DSGV's statement how banking customers could identify cards affected by the problems.