WASHINGTON, District of Columbia (AFP) - The Pentagon has informed the United States (US) Congress of a possible sale of US$2 billion (S$2.5 billion) worth of military equipment to Iraq, officials said on Friday.

Lawmakers, notified on Thursday, have 30 days to raise any objections to the plan, which consists of three contracts.

The first includes 12 Bell 412 EP helicopters and associated equipment, parts, training and logistical support totalling an estimated US$300 million.

"This equipment will provide the Iraqi Air Force with a search and rescue capability critical to developing a mature Air Force," the Defence Security Cooperation Agency, or DSCA, said in a statement.

The second contract, worth an estimated US$900 million, is for 50 M1135 Stryker Nuclear, Biological and Chemical Reconnaissance Vehicles.

The sale would provide the Iraqi army "with reliable capabilities for early warning of contamination by radiological, biological, and chemical material," according to the DSCA.

Worth some US$750 million, the final contract is for five years of maintenance support for a series of vehicles, from simple jeeps to so-called Tactical Floating River Bridge Systems.

"Helping Iraq maintain, sustain, and effectively utilise the equipment it has purchased or received from the US over the past decade is a US priority," the DSCA said.

As with all notifications of such plans, it underscored that the proposed sale would not "alter the basic military balance in the region."

In December 2011, US approved the sale of 36 F-16 fighter jets to Baghdad in a contract worth several billion dollars.

In October 2012, Iraqi Prime Minister Nouri al-Maliki had asked Washington, whose troops left the country at the end of 2011, to speed up delivery of weapons for Iraqi troops.

Baghdad had signed weapons contracts with Russia worth more than US$4.2 billion, but these were later cancelled on suspicion of corruption.