The United States on Tuesday approved a $2.2 billion sale of advanced battle tanks to Bahrain, a Gulf Arab ally once under an arms embargo over a crackdown on Shiite dissent.

The State Department said it had notified Congress it is ready to sell 50 M1A2 Abrams tanks, generally used for ground warfare, to the small island nation which has tense relations with nearby Iran.

"The proposed sale will improve Bahrain's capability to meet current and future threats by providing a credible force that can deter adversaries and provide the capability to participate in regional operations with the United States and other US partner nations," a State Department statement said.

Congress can still block the sale, although most military deals go through.

Bahrain is home to the US Navy's Fifth Fleet and is classified as a major non-NATO ally, giving it privileged defense cooperation with the United States.

Unique among Arab nations, Bahrain has signed on as a member of the coalition led by the United States and Britain that has struck Yemen's Iran-allied Huthi rebels over attacks on shipping carried out in professed solidarity with the Palestinians in the Israel-Hamas conflict.

Abrams tanks, among the heaviest in the world, are a mainstay of the US military.

President Joe Biden last year approved Abrams tanks to Ukraine to fight back Russian invaders, after initial concerns about the time needed to manufacture and train Ukrainian forces in the vehicles.

The State Department said that some 30 US contractors and one government official would be sent to Bahrain for up to five years to lead training.

Bahrain came under criticism in 2011 when, backed by fellow Sunni kingdom Saudi Arabia, it crushed an uprising led by the Shiite community that demanded a constitutional monarchy and an elected prime minister.

Then president Barack Obama imposed an arms embargo for four years. Bahrain returned to US good graces under former president Donald Trump, who hailed Bahrain's recognition of Israel.

Last year Biden's administration signed a new agreement with Bahrain to enhance defense and economic ties, including through greater intelligence-sharing.