Nuclear talks between Iran and six world powers appear no closer to a deal, and Iran's foreign minister says the other side is to blame.

Mohammad Javad Zarif says that the countries that Iran is negotiating with are changing their conditions. He says they are internally split, accusing them of using pressure tactics — something he says won't lead to a deal.

Zarif's comments Friday followed a U.S. warning that Washington is ready to walk away from the talks. The current round is now in its 14th day. The sides have given themselves until Friday to come to agreement after twice missing previous target dates.

The U.S., Russia, China, Britain, France and Germany are offering Iran sanctions relief in exchange for long-term, verifiable curbs on Tehran's nuclear activities.