MILWAUKEE (Reuters) - A top national security adviser to Donald Trump said on Wednesday that Taiwan needs to boost its defense spending significantly in the face of potential Chinese aggression.

The comments by Robert O'Brien, Trump's fourth and final national security adviser, follow remarks by the former president in which he said Taiwan should pay the United States for its defense.

Speaking to Bloomberg Businessweek in a June 25 interview published on Tuesday, Trump said: "I know the people very well, respect them greatly. They did take about 100% of our chip business. I think Taiwan should pay us for defense."

O'Brien, asked about Trump's comment at a Bloomberg Roundtable on the sidelines of the Republican National Convention in Milwaukee, said he believed Trump meant to indicate Taiwan should contribute more to its own defense.

"They've got to ramp up their spending to contend with the PRC and CCP, and we can help them, we can be part of that. But I think what President Trump is saying is ... we've got to have burden sharing," O'Brien told reporters, referring to the People's Republic of China and the ruling Chinese Communist Party.

He suggested Taiwan should consider spending at least 5% of its gross domestic product on its military to keep up with China, though he implied that figure was a rough estimate.

While O'Brien is not part of the Trump campaign and made clear he was expressing his personal views, he is in frequent contact with the former president on national security matters.

Washington has been eager to create a military counterbalance to Chinese forces, building on an effort known within the Pentagon as "Fortress Taiwan", as Beijing's military makes increasingly aggressive moves in the region.

Taiwan typically purchases weapons it receives from the U.S. rather than relying on aid, though America and its allies do have significant military assets in the region, which are intended in part to deter Chinese aggression against the democratically governed island that Beijing claims as its territory.

"If you look at the support that we have provided, the security cooperation that we have provided them over decades, it has been Taiwan actually purchasing military (equipment) from the United States," State Department spokesperson Matthew Miller told reporters on Wednesday.

"It has not been any way charity from the United States."

Taiwan's de facto embassy in Washington said preserving peace and stability in the Taiwan Strait is in the interest of the U.S. and the international community.

"Taiwan is doing its part by actively strengthening deterrence capabilities with the support of the United States under the Taiwan Relations Act," it said in a statement, citing the "threat of military coercion."

The Biden campaign did not immediately respond to a request for comment.

INCREASED DEFENSE BUDGET

Taiwan has significantly expanded its defense budget in recent years. From 2017 to 2023 its military spending rose to 2.5% of GDP from 2%, according to the U.S. Congressional Research Service. Taipei announced a defense budget for 2024 of about $19.1 billion.

But the island's overall level of spending still pales in comparison to China's massive outlays and the historic build-up of the People's Liberation Army, which dwarfs Taiwan's forces. In March, Beijing unveiled an annual defense budget of some $230 billion, a 7.2% increase on the year before, though analysts say actual spending is likely much greater.

The Democratic ranking member of the U.S. House of Representatives' bipartisan select committee on China, Raja Krishnamoorthi, called Trump's comments a betrayal.

"Failing to provide for Taiwan's defense would not only be potentially illegal under the Taiwan Relations Act, it would be a betrayal of American values and our democratic institutions," he said in a statement.

During the Trump administration, Washington agreed to sell billions of dollars worth of U.S. weaponry to Taiwan, but Taipei has complained of delays to weapons deliveries, including of Stinger anti-aircraft missiles.

(Reporting by Gram Slattery, Michael Martina and Simon Lewis; Editing by Don Durfee and Daniel Wallis)

By Gram Slattery, Michael Martina and Simon Lewis