WASHINGTON (REUTERS) - US House of Representatives Democrats investigating whether to impeach US President Donald Trump on Monday (Sept 30) issued a subpoena to his lawyer Rudy Giuliani, seeking documents related to dealings with Ukraine by Oct 15.

The Democratic-led House Intelligence Committee issued the subpoena in consultation with two other House panels and said in a statement that Giuliani had acknowledged on television that he asked the government of Ukraine to "target" former Vice President Joe Biden.

Democrats have been moving quickly since House Speaker Nancy Pelosi announced last Tuesday that she was formerly launching an impeachment inquiry.

On Friday, the three committees announced that Secretary of State Mike Pompeo had been subpoenaed, and depositions scheduled for five other State Department officials.

On Monday, Giuliani was asked to hand over documents related to Trump's effort to pressure Ukrainian President Volodymry Zelenskiy to investigate Biden, a top contender for the Democratic nomination to run against Trump as the Republican president seeks re-election in 2020.

"Our inquiry includes an investigation of credible allegations that you acted as an agent of the President in a scheme to advance his personal political interests by abusing the power of the Office of the President," the committee chairmen said in a letter to Giuliani.

They said Giuliani had stated that he had evidence such as text messages and telephone records, indicating that other Trump administration officials might have been involved in the scheme to put pressure on Ukraine to become involved in the 2020 election.

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Giuliani did not immediately respond to a request for comment.

Foreign Affairs Chairman Eliot Engel, Intelligence Chairman Adam Schiff and Oversight Chairman Elijah Cummings said letters were also sent seeking documents and setting deposition dates for three Giuliani associates, including businessman Lev Parnas and real estate investor Igor Fruman, who, according to various media accounts, helped introduce Giuliani into top Ukrainian political circles.

A letter was also sent to Semyon "Sam" Kislin, a Ukrainian immigrant who has had business ties to Trump and served on Giuliani's city economic development corporation when Giuliani was mayor of New York.

Parnas' deposition was set for Oct 10, Fruman's for Oct 11 and Kislin's for Oct 14.

In a letter, the committees asked the three to advise them by 5pm Tuesday, Oct 1, about whether they intended to comply with their requests for documents and to appear for the deposition.