WASHINGTON (NYTIMES) - Loyalists to US President Donald Trump have blocked transition meetings at some government agencies and are sitting in on discussions at other agencies between career civil servants and President-elect Joe Biden's transition teams, sometimes chilling conversations, several federal officials said.

At the Environmental Protection Agency (EPA), political appointees have joined virtually every discussion between career staff members and Mr Biden's team, monitoring conversations on climate change, scientific research and other topics. At the State Department such drop-ins are happening on what Mr Trump appointees define as an as-needed basis.

On Tuesday (Dec 8) Mr Biden's transition team was allowed for the first time into the National Security Agency, but at the United States Agency for Global Media, parent of Voice of America, the Trump-appointed leader is refusing to cooperate with the Biden transition team, two agency officials confirmed.

Presidential transition experts said the presence of political officials at agency handoff meetings was not unheard-of and could even be seen as helpful.

President George W. Bush, for example, worked closely in late 2008 with Mr Barack Obama's incoming team to help calm volatile financial markets. But against a backdrop of Mr Trump's refusal to concede election defeat, the actions of Mr Trump appointees appeared to be a pernicious effort to slow the transition, some experts said.

"The norm is that the political people are not involved in the nuts and bolts of this," said Professor Michael Herz, an exper on administrative law at the Cardozo School of Law at Yeshiva University.

He called the Trump administration's apparent determination to micromanage the transition process by overseeing meetings part of its broader plan to "milk their authority as long as they can and disrupt the new administration as much as they can."

Under the Presidential Transition Act, career employees play the primary role in managing the agency transitions, largely because they bring an institutional knowledge about the government functions and have been viewed as unpolitical stewards of the agencies they serve. No clear rules or guidelines, however, detail how the process should unfold.

During the handoff from Mr Obama's administration to Mr Trump, for example, political officials were explicitly disinvited from transition meetings, said Mr Thomas Burke, who served as EPA science adviser in the Obama administration at the time.

"To me, that's the equivalent of having the opposing coach sitting in the room as you're developing your team's strategy," he said.

Mr Myron Ebell, a senior fellow at the Competitive Enterprise Institute who led the Trump administration's transition for the EPA, agreed that Mr Obama's political appointees were not present but said he would have liked to meet with them. Regardless, he said, meetings were held in an open-plan office space.

The Biden transition team did not respond to a request for comment on the process. Several people close to the president-elect's team said that, after taking more than two weeks to begin the formal transition process, the Trump administration's handover has been fairly smooth and that Mr Biden is loath to disrupt that process by remarking on tensions.

So far, about 40 federal agency review teams have conducted more than 1,000 interviews and meetings, Mr Biden's transition officials said.

Federal employees who discussed the transition and asked to remain anonymous because they were not authorised to speak about the process offered mixed reviews on the presence of political leaders.

Several said they felt the Trump officials were implicitly intimidating employees from speaking openly about issues awaiting the new administration. Others described the meetings as merely awkward.

At the Department of Education, one official said Mr Trump appointees had not crashed briefings but said the written briefing materials given to Mr Biden's teams "gloss over anything controversial" and described the briefings as "politically influenced."

At the State Department, Mr Trump's appointees have insisted that they attend some, but not all, meetings of Mr Biden's transition team with career employees, according to an official familiar with the process.

It was not immediately clear if doing so was seen as broadly intrusive or stifling the discussions at the State Department, said the official, who spoke on condition of anonymity. However, the official said, including the outgoing administration's appointees in at least some diplomacy discussions was not unheard-of, and that, so far, the State Department personnel had been cooperative in accommodating the Biden team's requests.

Secretary of State Mike Pompeo has told department officials he was ready to meet with Mr Biden's transition team, CNN reported last week, and on Monday described the incoming administration as "plenty smart enough." That was a shift from late November, when he said in a Fox News interview that Mr Biden's foreign policy advisers "lived in a bit of a fantasy world" when they served during the Obama administration.

This week the Biden team was allowed into the Defence Intelligence Agency and the National Security Agency after several days of what two people close to the transition described as an effort by newly appointed Trump administration officials at the Pentagon to slow the transition by blocking access to Department of Defence intelligence agencies.

Ms Susan Gough, a Defence Department spokeswoman, said the agency sometimes adds personnel to the list of people with whom Mr Biden's team requests meetings "so that we have the right subject matter experts present," but she added, "there is no requirement that all meetings be attended by a political appointee."

No classified material has yet been given to Mr Biden's team, and it is not clear if or when that will be made available. Meetings at other intelligence agencies, including the National Geospatial-Intelligence Agency, are expected to come later.

On Tuesday, The Washington Post reported that Mr Michael Pack, a Mr Trump appointee who oversees the Voice of America and other federally funded news agencies, has declined to make records and personnel available to Mr Biden's team. At the EPA, Mr James Hewitt, a spokesman for the agency, confirmed that political leaders were attending meetings and said it was happening with the blessing of Mr Biden's transition team.