WASHINGTON - Some top Senate Democrats are questioning the wisdom of the U.S. asking the Cuban government to remove 60 percent of its staff from Washington, fearing it could provoke a diplomatic fight while the origin of sonic attacks in Havana remains unclear.

“The United States must be unrelenting in its efforts to protect our diplomats, investigate these disturbing incidents, and seek accountability for those responsible,” said Sen. Ben Cardin of Maryland, the ranking member of the Foreign Relations Committee.

“Although today’s decision to expel Cuban diplomats brings parity between U.S. and Cuban embassy personnel levels, I am concerned that it may also stoke diplomatic tensions and complicate our ability to conduct a thorough investigation of these attacks,” he said. “The U.S. should not take actions that could undermine our bilateral relations with Cuba and U.S. policies aimed at advancing our strategic national interests in the hemisphere.”

Cardin said he wants clarity during a Foreign Relations Committee briefing Wednesday. “In this time of uncertainty, the Administration and the State Department must consult with Congress before taking further actions,” he said in a statement.

Sen. Marco Rubio, R-Fla, is a member of the committee and has urged the State Department to seek the draw down at the Cuban Embassy. On Tuesday, Rubio scoffed at the idea Cuban authorities do not know what’s happening to American diplomats in Havana.

Sen. Bill Nelson, D-Fla, joined Rubio in calling for reciprocity. “With the loss of hearing and stroke-like-symptoms, theCuban government owes an explanation and reparations to the families ofthose injured and must work to ensure these attacks cease immediately.In the meantime, the Cuban Embassy’s staff in Washington, D.C. should bereduced by the same proportionate number of U.S. personnel recalled.”

But other Democrats say more proof is needed.

“We have a right and a duty to protect American diplomats serving overseas,” said Sen. Patrick Leahy, D-Vt. “But before we retaliate against another country by expelling their diplomats, we should have proof that they, and not a third country or party, harmed our citizens. We do not know who is doing this or why, yet we are punishing the Cubans for not preventing it. That will not help solve the mystery of this serious offense, and it won’t make our diplomats safer. We are in the early stages with Cuba on most issues, and the Cuban government has shown a willingness to discuss concerns that had not been broached before. This will slow those discussions to a trickle.”

Democratic Rep. Kathy Castor of Tampa had other worries.

“I strongly support U.S. and Cuban efforts to determine who is responsible for the harmful sonar attacks as they must be held accountable,” she said Friday when the U.S. announced it would pull employees in Havana.

“I am concerned however that today’s announcement and indefinite suspension of visa processing and consular services goes too far and unnecessarily harms the ability of Cuban and American families to travel and see loved ones,” Castor added. “The State Department must swiftly develop contingency plans to continue to allow families to travel from the island. Many of my neighbors who have been waiting for the opportunity to reconnect with loved ones now face unnecessary and heartbreaking barriers. Cuba, Florida and many Caribbean islands and nations are recovering from devastating hurricanes and families should not be subjected to unnecessary and costly burdens and red tape when trying to visit and stay with family.”