190211Acting Pentagon chief Patrick Shanahan
Acting Pentagon chief Patrick Shanahan (centre L) takes part in a meeting with Afghan National Security Adviser Hamdullah Mohib (R), next to General Scott Miller (centre R), commander of US and NATO forces in Afghanistan, and US Ambassador to Afghanistan John Bass (L) in Kabul. Acting Pentagon chief Patrick Shanahan arrived in Afghanistan on an unannounced visit February 11 as the United States leads a push for peace talks with the Taliban. Image Credit: AFP

Washington: The Pentagon said Friday it was diverting another $1.5 billion for new barriers to stop illegal immigrants on the US-Mexico border, following the authorization of $1 billion in March.

Acting Defense Secretary Patrick Shanahan has agreed to take charge of the replacement of 125 kilometres of fencing on the southern frontier in Arizona and Texas, the defence department said in a statement.

"The funds were drawn from a variety of sources, including cost savings, programmatic changes and revised requirements," spokesman Tom Crosson said.

"This transfer of funds will not affect military preparedness, nor impact service member benefits."

Frustrated by Congress's refusal to provide the budget he wanted to build a wall, President Donald Trump declared a national emergency on the border in February, asking to repurpose $6 billion from military funds.

In March Shanahan authorised $1 billion to construct 92 kilometres of 18-foot high barrier, improve roads and install lighting.

The Pentagon has been under pressure to show it is not diverting the funds from combat missions or other vital work.

Shanahan said some of the diverted money came from unspent funds in Afghanistan.

"We found ways to do this without having any impact on readiness," he said, adding that "I won't be reprogramming any more money for the border wall."