President Donald Trump on Thursday said he plans to nominate acting Defense Secretary Patrick Shanahan to that position permanently , five months after the former Boeing executive ascended to the role following then-Pentagon chief Jim Mattis' resignation late last year.

"I am honored by today's announcement," Shanahan said in a statement, adding he plans to "continue the aggressive implementation" of the signature Pentagon strategy Mattis created during his tenure. "I remain committed to modernizing the force so our remarkable soldiers, sailors, airmen and Marines have everything they need to keep out military lethal and our country safe."

Shanahan served as deputy secretary starting in July 2017 with a portfolio that largely governed bureaucratic and domestic issues until Mattis' resignation following Trump's stated intention in December to withdraw all U.S. forces from Syria. Trump indicated his intention to nominate Shanahan to the top job at the Defense Department, but the process was stalled while the Pentagon's inspector general investigated whether he inappropriately used his influence to promote the business interests of his former employer and undermine its competitors.

The inspector general cleared Shanahan of any wrongdoing in late April, eliminating what had been considered the largest obstacle to Trump's nominating him. His history at Boeing, where he worked since 1986, became a central line of questioning at his confirmation hearing to become deputy secretary. Former Sen. John McCain, a Republican from Arizona, saying he needed from Shanahan confidence that "the fox is not going to be put back into the henhouse."

Trump's use of executive power to deploy the military has become fraught among his critics in Congress, chiefly his decisions to send thousands of soldiers to the southern U.S. border to contain what he considers a migration crisis. Trump also overrode Congress' refusal to fund his latest budget request for a border wall by dispatching military engineers and tapping other military construction budgets to pay for a barrier.

Shanahan has been at the center of these debates in recent months, telling the Senate Defense Appropriations subcommittee earlier this week that the Pentagon has allocated funding to build 256 miles of barrier.

White House spokeswoman Sarah Sanders said in a statement late Thursday that Trump made the decision to nominate Shanahan "based upon his outstanding service to the country and his demonstrated ability to lead."