Under Nicaraguan law, the National Assembly must give permission for visits and military exercises involving foreign states in the Latin America country. The Nicaraguan opposition has prevented parliament from working since November over claims of vote rigging in local elections.
"I am performing my duties, and we are preparing to meet the Russian warships, which will enter Nicaragua's territorial waters in the next few hours," Daniel Ortega told military officials.
He said it was his duty to step in and implement the law while parliament is paralyzed by the opposition which he said is refusing to comply with the law.
Russia's Admiral Chabanenko missile destroyer and two support ships are to visit the port of Bluefields in Nicaragua on December 12-15 following a joint naval exercise with Venezuela and a visit to Panama.
The head of state issued a decree on December 9 authorizing the visit by the Russian ships with up to 650 troops on board to participate in exercises with Nicaragua's military. The decree was published in a government paper and submitted to parliament.
Wilfredo Navarro, of the opposition Constitutionalist Liberal Party, said the arrival of the Russian ships without parliamentary approval would be a breach of the Constitution and should be prevented by Nicaragua's Armed Forces.
The Russian Udaloy class destroyer made a round trip through the Panama Canal on December 6, becoming the first Russian or Soviet warship to enter the waterway since World War II. Russia, which announced last year that its Navy had resumed and would continue to build up a constant presence throughout the world, currently has three naval task groups on tours of duty in the world's oceans.
Nicaragua is the only country to back Russia in recognizing the breakaway regions of South Ossetia and Abkhazia as independent states following a brief Russian-Georgian conflict in August.
Ortega enjoyed Moscow's support in the 1980s after the Sandinista National Liberation Front overthrew the then dictator Anastasio Somoza in 1979. Ortega was elected president in 1985 and served until 1990. Ortega won presidential elections in 2006.