Aug 7 (Reuters) - U.S. Secretary of State Antony Blinken accused Nicaraguan President Daniel Ortega of taking new "undemocratic, authoritarian actions" after police arrested another rival politician ahead of elections later this year. Singling out both Ortega and his wife Rosario Murillo, who holds the position of vice president, Blinken said in a statement on Saturday that the pair were seeking to hold on to power "at all costs" with a strategy of disqualifying potential opposition candidates. "The United States views the regime"s latest undemocratic, authoritarian actions — driven by Ortega"s fear of an electoral loss — as the final blow against Nicaragua"s prospects for a free and fair election," Blinken said. The Central American country"s presidential election in November has already "lost all credibility", the statement said. Ortega"s office did not immediately respond to a request for comment. On Wednesday, police put opposition politician Berenice Quezada under house arrest, accusing her of inciting hatred and violence. A former beauty queen turned Ortega critic, Quezada had been tapped last week by the Citizens Alliance for Liberty Party, or ACXL, to be the running mate of Oscar Sobalvarro. read more Ortega, a former Marxist guerrilla who has turned against many of his one-time rebel allies, is seeking to retain his grip on power with a fourth consecutive term. His government has in recent months repeatedly detained political adversaries, including to date seven presidential hopefuls plus a couple dozen other opposition figures. Many have been accused of undermining Nicaragua"s independence and sovereignty, and banned from running for office. On Friday, the U.S. State Department imposed visa restrictions on 50 relatives of Nicaraguan officials, including family members of lawmakers, prosecutors and judges. read more