Washington: Acting Pentagon chief Patrick Shanahan said Monday he had authorized $1 billion to build part of the wall sought by President Donald Trump along the US-Mexico border.

The Department of Homeland Security asked the Pentagon to build 92 kilometers of 5.5-meter fencing, build and improve roads, and install lighting to support Trump's emergency declaration as concerns the border. 

Shanahan "authorised the commander of the US Army Corps of Engineers to begin planning and executing up to $1 billion in support to the Department of Homeland Security and Customs and Border Patrol," a Pentagon statement read.

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Just before Shanahan was scheduled to testify in Congress to present and defend the Pentagon's draft budget, the statement was released. 

However, the decision didn’t go down well with everyone, especially the opposition Democrats and fellow Republicans. They argue that the action will be an abuse of presidential powers. Moreover, they are afraid that it will set a negative example. 

Shanahan recently made headlines as he was being investigated by the Pentagon's inspector general for alleged bias in acquisitions toward his former employer, Boeing.

Investigators are seeking to see if Shanahan, as deputy defense secretary, had violated ethics rules by disparaging Boeing rival Lockheed Martin in meetings at the Pentagon.

With agency inputs