The call -- in which Donald Trump tried to get Volodymyr Zelensky to provide dirt on a 2020 election rival -- has sparked an impeachment inquiry into the US president.

Congress, which needs to approve the transaction, has been notified about the possible $39.2 million sale of 150 Javelin missiles and 10 launch units, the Defense Security Cooperation Agency (DSCA) said in a statement.

"This proposed sale will contribute to the foreign policy and national security of the United States by improving the security of Ukraine," the DSCA said.

"The Javelin system will help Ukraine build its long-term defense capacity to defend its sovereignty and territorial integrity in order to meet its national defense requirements. Ukraine will have no difficulty absorbing this system into its armed forces," it added.

According to a White House memorandum on the July call between Trump and Zelensky, the Ukrainian leader said that "we are almost ready to buy more Javelins from the United States for defense purposes."

In the same call -- which took place after Trump froze military aid to Ukraine, which is battling Russian-backed separatists -- the US president urged Zelensky to investigate Democratic frontrunner Joe Biden and his son Hunter.

That has led the Democratic-controlled US House of Representatives to launch an impeachment inquiry that is threatening Trump's presidency.