A majority of the Dutch who voted in Wednesday's referendum rejected the European Union trade deal with Ukraine, but exit polls showed the turnout may have been too low to be valid.
The exit polls, carried out by polling institute Ipsos, showed 64 percent of those who voted said "no" to the deal, with some 36 percent voting in favor.
But it was not immediately clear if turnout had reached the 30 percent of the 12.5 million eligible voters needed to be valid.
The exit polls initially put turnout at 29 percent, before updating it to 32 percent with a margin of error of 3 percent.
The referendum is nonbinding, but it will be an important measure of EU support. It comes just three months before British voters cast ballots on whether to remain in the European Union.
Dutch opponents of the EU agreement say its ultimate goal is to bring Ukraine, which struggles with corruption and an ongoing separatist movement, into the bloc. Supporters say the agreement would aid economic development on both sides and improve human rights in the former Soviet republic.
The United States backs the deal. State Department Deputy Spokesman Mark Toner said Wednesday that it is "in the interests of the United States, of the Netherlands, of the EU to help ensure that Ukraine becomes a democratic and economically stable country."
Ukraine's president, Petro Poroshenko, has urged Dutch voters to say "yes" to the agreement.
Whether or not the Netherlands' voters approve or reject the agreement, it is expected to send an important signal to the Dutch government about the citizens' attitudes toward the European Union, which is struggling to cope with economic woes, political divisions, and the worst refugee crisis since World War II.