Democratic lawmakers could vote this week on articles of impeachment against U.S. President Donald Trump, the House Judiciary Committee chairman said on Sunday as lawmakers sharpened their focus on charges of wrongdoing in his dealings with Ukraine. 

U.S. Representative Jerrold Nadler said the panel will not decide on the specific articles until after a hearing on Monday to consider evidence gathered by the House Intelligence Committee in its investigation of the Republican leader. 

"There are possible drafts that various people are writing," Nadler told CNN's "State of the Union." "But the fact is we're not going to make any decision as to how broad the articles should be – as to what they contain, what the wording is – until after the hearing tomorrow."

The Democratic-led House of Representatives' impeachment inquiry focuses on Trump's request that Ukraine investigate former Vice President Joe Biden, a leading contender for the Democratic nomination to face Trump in the November 2020 election. 

Nadler told NBC's "Meet the Press" that articles of impeachment would be brought to the panel later in the week. Asked on CNN if lawmakers could vote this week, he said, "It's possible."

The impeachment probe has focused on a July 25 telephone call in which Trump asked Ukrainian President Volodymyr Zelensky to open an investigation into Biden and his son Hunter, and into a discredited theory promoted by Trump and his allies that Ukraine, not Russia, meddled in the 2016 election. 

Democrats cite "overwhelming" evidence that Trump put his personal interests above those of the country in seeking foreign help to win the November 2020 election. 

"I think the case we have, if presented to a jury, would be a guilty verdict in about three minutes flat," Nadler said. 

Trump called the impeachment proceeding a "hoax" on Sunday, accusing Democrats of changing the guidelines "because the facts are not on their side." 

"When you can't win the game, change the rules!" Trump tweeted. 

Nadler's remarks came a day after the majority staff of the House Judiciary Committee released a report explaining what they called constitutional grounds for Trump's impeachment. 

According to the nation's constitution, the House shall have the sole "Power of Impeachment," while the Senate shall have the sole "Power to try all impeachments." 

Trump will be impeached if the House approves any of the articles of impeachment the House Judiciary Committee has recommended by a simple majority vote. 

But conviction can only happen in the Senate and requires at least two-thirds of its members, or 67 senators, to vote in favor. Currently, the Senate has 53 Republicans, 45 Democrats and two independents. 

Senator Lindsey Graham, a Republican, told Fox News on Sunday that he thinks the impeachment trial is "going to meet a quick end in the Senate." 

(With input from Reuters, Xinhua)