Seventeen members of the US Congress asked Defense Secretary Lloyd Austin to speed up the Pentagon's review of Ukraine's request for large combat drones, according to a letter dated Wednesday, Reuters reports.

 US President Joe Biden's administration's plan to sell four large drones to Ukraine reportedly hit a roadblock in June amid fears the sophisticated equipment could end up in enemy hands.

 The paper's sources said the technical objection to the sale was raised during a deeper review by the Pentagon's Defense Technology Security Administration, the group responsible for keeping expensive technology out of enemy hands.

 Earlier, a plan to sell MQ-1C Gray Eagle drones, which have been in circulation since March, was approved by U.S. officials, three of the people said.

 "Thorough risk assessment should not come at the expense of Ukrainian lives," says the letter from the environment, signed by a bipartisan group of the US Congress, which calls for the Pentagon's review of whether it can transfer weapons to be completed "in a timely manner."

 The letter, signed by Republicans and Democrats, refers to Ukraine's recent territorial gains and adds that "the use of more powerful unmanned aerial systems on the battlefield will allow the Armed Forces to better hold the territory they fought so hard to regain."