WASHINGTON — The United States should delay the sale to Bahrain of any items in a proposed $53 million weapons package that could be used against protesters there, a US senator said Thursday.

"I urge the administration to delay the sale of any items within the proposed weapons package that could be used to disrupt peaceful dissent," Republican Senator Marco Rubio said in a letter to Secretary of State Hillary Clinton.

Rubio said Washington should for now withhold items "that could be use to disrupt, monitor, or otherwise restrict the Bahraini people's right to peacefully assemble and petition their government."

The senator's letter came as pressure mounted in the US Congress against the proposed sale after Bahraini security forces in mid-March crushed a month-long protest that authorities say left 24 people dead, including four policemen.

The opposition puts the death toll at 31.

US lawmakers were shocked in January when it came to light that tear gas used against Egyptian demonstrators against deposed president Hosni Mubarak was found to be "Made in America."

Since then, some have sought tighter restrictions on weapons and non-lethal equipment provided to Middle Eastern governments that could be used against protestors in the so-called "Arab Spring" pro-democracy movement.

Bahraini opposition groups called in a new declaration on Wednesday for an elected government and for ending discrimination against the Sunni-ruled country's Shiite majority.

The crackdown saw authorities sweep through Shiite villages, arresting hundreds, and scores were dismissed from their jobs.

Hundreds are being tried by a special security court, and dozens more have received lengthy jail sentence, while at least five were sentenced to death.

A group of Democratic senators on Wednesday urged Clinton to delay the arms sale, warning it "would weaken US credibility at a critical time of democratic transition in the Middle East."

"We urge you to send a strong signal that the United States does not condone the repression of peaceful demonstrators by delaying the possible arms sale" until Bahrain frees all political prisoners and seeks political reforms, they said.

Democratic Senators Bob Casey, Richard Durbin, Benjamin Cardin, Robert Menendez, and Ron Wyden signed the letter.

Wyden and Democratic Representative James McGovern last week introduced legislation to bar arms sales to the kingdom until it addresses "alleged human rights violations" since February.