The top Democrat on the Senate Foreign Relations Committee wrote three letters to federal government officials seeking more information about the withholding of security funding for Ukraine, the subject of a whistleblower complaint involving a phone call between President Trump and Ukrainian President Vlodomyr Zelensky in July.

Senator Robert Menendez of New Jersey sent a letter to the State Department's internal watchdog to ask for a review of the matter and he also wants to know how aware the State Department was of the decision to withhold the funding.

"If the president withheld funds to extract commitments by the Ukrainian government to take action against a political opponent of the president, it would constitute an unacceptable abuse of power and subversion of U.S. foreign policy and foreign assistance funds under the purview of the State Department for the personal use of the president," Menendez wrote to Inspector General Steve Linick.

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Menendez also wrote to Secretary of State Mike Pompeo to demand records regarding any support provided by the department to Trump personal lawyer Rudy Giuliani, who has been urging the Ukrainians to investigate Joe Biden and his son, Hunter Biden and their connections to Ukraine.

"[A]t the moment, it remains an open question whether the Administration has altered its policy towards Ukraine or demanded specific action from a foreign nation to fulfill the President's expressed wishes about a domestic political opponent," Menendez wrote to Pompeo.

Giuliani had at one point planned to travel to Ukraine to speak with Zelenksy in person to make his case. He had told The New York Times it was his right to travel to Ukraine to "defend" his client — to try to push for investigations he thought could be "very helpful" to the president.

The New Jersey senator also wrote to Office of Management and Budget Acting Director Mick Mulvaney to ask him to explain to Congress why it failed to take action on Ukraine's security assistance funding for over two months.

"As it is becoming clear that the president in fact pressured Ukrainian officials, we must immediately understand whether, and to what extent, the president and his team converted duly-appropriated United States foreign assistance funds for his personal and political benefit," Mendendez pressed.