Top U.S. diplomats encouraged Ukraine's president to launch investigations into the 2016 U.S. election and the energy company that employed the son of 2020 Democratic candidate Joe Biden, in exchange for a face-to-face meeting with President Donald Trump, according to texts released Thursday, The Washington Post reported.

The texts, provided to Congress by Kurt D. Volker, the State Department's former special envoy for Ukraine, came from a series of early September exchanges, The New York Times reported.

The texts reveal the diplomats believed Trump would not meet with President Volodymyr Zelensky unless the Ukrainian president promised publicly to launch investigations, according to the Post. The texts do not mention Biden by name, the newspaper reported.

According to the newspaper, Volker, in a text message to Zelensky aide Andrey Yermak on the day of a July 25 phone call between Trump and Zelenskiy, wrote, “Heard from 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.”

The text messages were released by Democrats on the House Intelligence Committee late Thursday, CNN reported.

A memo detailing the transcript of the telephone call between Trump and Zelensky was released by the White House last week.

One text message, written by William D. Taylor, a top U.S. diplomat in Ukraine, on Aug. 9 raised concerns about withholding military aid until Zelensky launched an investigation, the Post reported.

“Are we now saying that security assistance and WH meeting are conditioned on investigations?” Taylor texted to Gordon D. Sondland, the U.S. ambassador to the European Union.

Another text by Taylor a month later raised more concerns, the Times reported.

“As I said on the phone, I think it’s crazy to withhold security assistance for help with a political campaign,” Taylor texted Sept. 9 to Volker and Sondland, the U.S. ambassador to the European Union.

"The president has been crystal clear no quid pro quo's of any kind," Sondland texted back, according to the Post. "The president is trying to evaluate whether Ukraine is truly going to adopt the transparency and reforms that president zelensky promised during his campaign I suggest we stop the back and forth by text."

The text messages came to light after a nine-hour, closed-door session between congressional investigators and Volker, the Times reported.

Trump has said he wanted Zelensky to investigate Biden and his son, Hunter Biden, the newspaper reported.