The US secretary of state, Mike Pompeo, has insisted that the state department behaved appropriately in its dealings with the Ukrainian government and Donald Trump’s lawyer, Rudy Giuliani.

Democrats called Pompeo’s response inadequate and called on him to appear before Congress, arguing that department officials would have been privy to a July call between Trump and Ukrainian president, Volodymyr Zelenskiy.

Two US diplomats are mentioned in the whistleblower report on Trump’s relations with Kyiv released on Thursday: the part-time special envoy Kurt Volker and the ambassador to the EU, Gordon Sondland. According to the report they traveled to Ukraine the day after the critical Trump-Zelenskiy call to meet the Ukrainian president.

The whistleblower report said that the two diplomats had “provided advice to the Ukrainian leadership about how to ‘navigate’ the demands that the president had made of Mr Zelenskiy”.

The report also said they also gave advice on how to “understand and respond to the differing messages they were receiving from official US channels on the one hand, and from Mr Giuliani on the other”.

State department officials have confirmed that Volker helped Zelenskiy’s office get in touch with Giuliani.

Questioned about the involvement of state department officials in connecting the Kyiv government with Giuliani, Pompeo sought to play down the importance of the whistleblower report.

“I haven’t had a chance to actually read the whistleblower complaint yet. I read the first couple of paragraphs, but I got busy today,” Pompeo told reporters in New York where he is attending the UN general asssembly.

“But I’ll ultimately get a chance to see it. If I understand it right it was someone who has secondhand knowledge,” the secretary of state said.

“But what I’ll say this morning about the engagement of the state department is: to the best of my knowledge, and from what I’ve seen so far, each of the actions that were undertaken by state department officials is entirely appropriate and consistent with the objective that we had.”

He added: “Certainly, since we have come into office, we’re trying to use this opportunity to create a better relationship between the United States and Ukraine, to build on opportunities to tighten our relationship and to help end corruption in Ukraine.”

The top Democrat on the Senate foreign relations committee, Bob Menendez, said Pompeo’s responses had been inadequate and called for him to appear before the committee.

Menendez said in a tweet that the whistleblower report “shows senior state department officials were both on the line AND briefed after Trump’s call pressuring Ukraine’s government.

“[Secretary Pompeo] must appear before the Senate foreign relations committee immediately to explain his agency’s role in this mess.”

Pompeo cut short questions at his press conference and was not asked about his own role in adding credence to Trump’s allegations about the Biden family and cutting short the posting of the former US ambassador to Kyiv Marie Yovanovitch in May after she was attacked by rightwing media for being anti-Trump.

In his July call to Zelenskiy, Trump referred to her disparagingly as “the woman”, calling her “bad news”, and adding, darkly and mysteriously: "she’s going to go through some things”.

“Yovanovitch was slimed,” said Daniel Fried, former secretary of state for European and Eurasian affairs. “The way she was treated was disgraceful. I have known her for 25 years and she is careful, scrupulous, and professional. She is someone who does not freelance. She is a straight arrow.”

Fried, now at the Atlantic Council, said that aides to the former president Petro Poroshenko had denounced Yovanovitch to their allies in the conservative US press, because she had been highly critical of the failure to prosecute corruption aggressively.

A former official familiar with the sequence of events said Zelenskiy’s office began trying to organise a summit meeting with Trump soon after his election in April. With the help of the US embassy, a tentative plan was put together for the two leaders to meet at a conference on Ukrainian reform in July.

The White House pulled out of that event and suggested a White House meeting in late July. That date was then postponed. Meanwhile Giuliani approached the US embassy in Kyiv asking for ways of connecting to Zelenskiy’s inner circle but he was rebuffed by Yovanovitch.

“Giuliani reached out in the spring, but they stiffed him,” the former official said, adding that Trump’s lawyer was trying to persuade the new Zelenskiy government to look into the activities of Burisma Holdings, where Hunter Biden had a seat on the board. When Zelenskiy’s entourage was not responsive, military aid to Ukraine was suspended in July, just before Trump’s second call to the Ukrainian president.

“The weapons were added as an effort to persuade them further,” a former official said.

Another former official with knowledge of current Washington-Kyiv relations said: “Masha [Yovanovitch] was suspect because she was very critical of the lack of anti-corruption prosecutions. And I think she stiff-armed Giuliani, and wouldn’t help him. Being a professional, she didn’t want to play political games.”

The American Foreign Service Association issued a statement on Thursday demanding that the service of US diplomats “not be politicised, and that they not be dragged into partisan political battles”.

Fried said that he had sympathy for Volker and Sondland, who had been put in a difficult situation, under pressure from Trump to connect Zelenskiy with Giuliani to dig up compromising material on Biden and his son Hunter.

“The state department people mentioned come off well. They tried to contain the damage. In their place I might have done the same,” he said. “They were trying to help Ukraine maintain good relations with the US while doing what they could to satisfy Trump, without crossing any lines.”

Another former colleague of Volker’s was less charitable.

“I think Kurt is trying to have his cake and eat it,” the former official said. Volker’s role as envoy is unpaid and part-time. He has kept his job as director of the McCain Institute for International leadership at Arizona University, and, according to MSNBC news on Thursday, had at the same time worked for a lobbying firm with international clients. “He is getting drawn into corrupt efforts that are incompatible with his diplomatic role. He should consider resigning.”

The state department and the McCain Institute had not responded to requests for comment at the time of publication.