The voting on Friday on the motion to call witnesses was 51 against and 49 for, with two Republicans joining the Democrats.
The outcome was a nail-biter with the last of four wavering Republicans, Lisa Murkowski, announcing her decision to oppose the call for witnesses only minutes before the trial resumed on Friday.
The Democrats had wanted to call John Bolton, a former national security adviser who was dismissed by Trump, to testify about the military aid to Ukraine that he froze.
The witness decision opens the way for the Senate to vote its verdict on the charges of abuse of power and obstruction of Congress.
As has been clear from the beginning, Trump will be acquitted because a two-thirds of the Senators in the Republican majority Senate will have to vote to convict him.
The Democrats were using the impeachment process as campaign tool for the November election to discredit Trump among his supporters and the undecided voters.
Republican Senate majority leader Mitch McConnell like Trump wanted a quick end to the trial in time for the president's State of the Union Address on Tuesday.
However, the final vote will be pushed to Wednesday evening, Republican Senator Roy Blunt told reporters after a meeting of the party senators.
He said that the Senate will meet on Monday for final arguments by the prosecutors and Trump's lawyers and then allow senators to speak about their stand on impeachment till the verdict vote.
Blunt said that Democratic leader in the Senate Chuck Schumer was on board with the arrangement.
But Schumer, who called the vote against witnesses "a tragedy on a grand scale" and a "perfidy,a can bring up several procedural issues to stall the final verdict.
"We'll see, we'll see," he told reporters cryptically.
The charges of abuse of power arise from Trump asking Ukrainian President Volodymyr Zelentsky to investigate the dealing of former Vice President Joe Biden and his son, Hunter, in that country.
The Democrats say that this was inviting a foreign country to intervene in US elections and was compounded by freezing military aid to Ukraine.
Republicans point out that the appointment of Hunter Biden to the directorship of a Ukrainian gas company with monthly payments of over $50,000 when he had no experience in the areas and the former vice president having the prosecutor looking into the company removed were unethical.
The Senate had voted down Democrat demands for calling witnesses at the start of the trial last week, but it received renewed momentum from disclosures that Bolton had written in a manuscript for a yet to be published book that Trump had linked the aid freeze to the probe of Bidens.
The news about the book was broken by The New York Times on Sunday in the middle of the trial.
Trump has denied that he had linked aid to the probe and Bolton was saying that sell his book.
Trump's lawyers said that the aid was withheld only to ensure that the new president was committed to fighting corruption and getting other European countries to pitch in.
Adam Schiff, the leading prosecutor from the House of Representatives that impeached Trump, said that without witnesses the trial would be unfair.
The House voted last month to impeach Trump and have the Senate try him.
Trump's lawyer Jay Sekulow said that calling witnesses would cause a long delay in the trial.
He said that Trump's lawyers had been shut out of the impeachment investigation and hearings and the Republicans in the House were barred by the Democrats from calling their own witnesses.
If new witnesses were called, he said Trump's defence team could call the witnesses from the House hearings and cross examine them in the Senate.
Trump's Legislative Director Eric Ueland said that they were pleased with the outcome of the vote.
(Arul Louis can be contacted at arul.l@.in and followed on Twitter @arulouis)
( With inputs from IANS )