U.S. acting Secretary of Defense Christopher Miller on Wednesday praised the United Kingdom for its planned significant increase in military spending, an investment the equivalent of almost $21.9 billion, which will be the largest for the nation in 30 years. 

The increase was announced by Prime Minister Boris Johnson on Wednesday during the ongoing Brexit transition period, in what Johnson framed as "our chance to end our era of retreat."

"The US Department of Defense applauds the announcement by the United Kingdom to significantly increase defense spending," Miller said. "The UK is our most stalwart and capable ally, and this increase in spending is indicative of their commitment to NATO and our shared security."

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The increase in defense spending comes after years of President Trump pressuring NATO allies to invest in their militaries and signals that the limited success the president has had in that area during his term could continue to build even with President-elect Biden set to assume office in less than two months. 

"The defence of the realm is the first duty of government," Johnson said in a tweet. "We are investing an extra £16.5 billion in defence to end the era of retreat, strengthen our Armed Forces, and extend British influence as a force for good in the world."

Miller added: "With this increase, the UK military will continue to be one of the finest fighting forces in the world. Their commitment to increased defense funding should be a message to all free nations that the most capable among us can – and must - do more to counter emerging threats to our shared freedoms and security.”

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According to the U.K. government, the spending increase will "cement" its position first in Europe in defense spending and second in NATO, behind only the United States. 

Fox News' Lucas Tomlinson and Jennifer Griffin contributed to this report.