Washington (CNN)Text messages released on Thursday between US diplomats and a senior Ukrainian aide show how a potential Ukrainian investigation into the 2016 election was linked to a desired meeting between Ukrainian President Volodymyr Zelensky and US President Donald Trump. The text messages, which were released by the House Intelligence Committee, underscore how Trump’s personal attorney, Rudy Giuliani, was closely connected to US policy on Ukraine and was involved in setting up the July 25 phone call between Trump and Zelensky, in which Trump also urged an investigation into former Vice President Joe Biden and his son, Hunter Biden. They show how cognizant the Ukrainians were about the importance of the election investigation to Trump and Giuliani’s role. On the morning of the call, in an exchange with a key adviser to the Ukrainian President, then-US Special Envoy for Ukraine Kurt Volker made clear that it was important to the White House that Zelensky convince Trump that an investigation into the 2016 election would happen. “Heard from the White House — assuming President Z convinces trump he will investigate/’get to the bottom of what happened’ in 2016, we will nail down date for visit to Washington,” Volker said via text to the Ukrainian adviser on the morning of July 25. Volker provided Congress with the text messages ahead of his closed-door congressional testimony on Thursday before three committees leading the House’s impeachment inquiry into Trump and Ukraine. The messages released by Democrats on the House Intelligence Committee add a new layer of detail to the whistleblower complaint that prompted the impeachment inquiry, which alleged that Trump had urged the Ukrainian government to dig up dirt on his political rival, Democratic presidential candidate Joe Biden. That Trump wanted an investigation was a message that seemed to register with the Ukrainian administration. Volker and the Ukrainian adviser, Andrey Yermak, continued to text after the call about Zelensky making a public statement ahead of a meeting between the two leaders. “I think potus really wants the deliverable,” US Ambassador to the European Union Gordon Sondland texted Volker on August 9, as the two were talking about possible dates for a meeting. “Once we have a date, will call for a press briefing, announcing upcoming visit and outlining vision for the US-UKRAINE relationship, including among other things Burisma and election meddling in investigations,” Yermak wrote to Volker the following day.