Turkish President Recep Tayyip Erdogan on Monday expressed sadness over a decision by the US embassy to stop all regular visa services in Turkey amid a boiling diplomatic row.

"Above all, this decision is very, very saddening. For the Ankara (US) embassy to take a decision like this, to put into practice is saddening," Erdogan said in his first reaction to the decision, at a news conference with Ukrainian counterpart Petro Poroshenko in Kiev.