HALIFAX, Nova Scotia — The top White House official for national security would not say Saturday whether President Donald Trump's concerns about corruption in Ukraine have been satisfied, declining to answer a direct question about whether the U.S. would provide military aid to Kyiv next year.

Speaking to a group of reporters on the sidelines of an international security conference here, national security adviser Robert O'Brien demurred when asked specifically whether current corruption levels in Ukraine could yet again threaten almost $400 million in annual military aid the U.S. supplies as a critical bulwark for Kyiv's ongoing conflict with Russia.

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In response to a question about whether the U.S. would provide aid next year, O'Brien instead spoke generally on the importance of ensuring that taxpayer dollars don't end up being misspent.

"We've got men and women in the U.S. who are working very hard," O'Brien said. "When we take U.S. tax dollars and send them overseas, we always want to make sure we do our best to make sure there's not corruption, that those tax dollars are not going to line the pockets of some [dictator] or used for some corrupt purposes."

"That's sacred money that's coming from some single mom who's working a job and paying her taxes, and we're going to now send it to Ukraine instead of sending it back to Detroit or Chicago or somewhere else?" he said.

He added that Trump "is always concerned about corruption. That goes beyond Ukraine, that's any form of foreign aid."

Trump has said his unilateral and controversial decision to withhold military aid to Ukraine this summer centered on concerns about corruption there. His decision came even after the Pentagon certified in May that Ukraine "has taken substantial actions to make defense institutional reforms for the purposes of decreasing corruption [and] increasing accountability," according to a letter to Congress that NPR obtained. The certification is required by law.

A congressional impeachment inquiry is currently considering whether that temporary hold-up was part of a quid pro quo to get Ukrainian President Volodymyr Zelenskiy to investigate a Trump political rival, namely Democratic presidential candidate Joe Biden, whose son Hunter Biden previously served on the board of a Ukrainian gas company.

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The issue of U.S. support for Ukraine, which has traditionally drawn unusual bipartisan support in Congress, has now become intensely politically charged in recent weeks, particularly following last week's impeachment hearings in the House of Representatives.

Ukrainian Minister of Defense Andrii Zagorodniuk, also in attendance at the conference, did not respond to multiple requests for interviews.

Sen. Jim Risch, the chairman of the Senate Foreign Relations Committee and the leader of a congressional delegation to the conference here, declined to answer earlier on Saturday when asked if he believes provocative assertions Trump has made in recent days without providing evidence that it was Ukraine that interfered in the 2016 presidential election – not Russia as U.S. intelligence agencies have concluded. The Idaho Republican said he would not comment on the issue until after the impeachment proceedings are over.