President Donald Trump's budget office director Thursday defended the agency against claims from the Joe Biden transition team the agency is obstructing to transition process.

Office of Management and Budget Director Russell Vought sent a letter to Ted Kaufman, head of the transition team, saying his office has taken more than 45 meetings with the Biden team, but does not have the responsibility to work with them to dismantle Trump's efforts while he is still in office.

Vought, has argued internally the agency needs to focus on finishing new regulations the Trump administration plans to publish before the president leaves office, according to people familiar with the matter.

"It is appropriate for OMB to share information about ongoing programs so the BTT can use it to develop its own policies," Vought wrote. "We have provided all information requested from OMB about ongoing programs. To your specific criticisms with respect to COVID, as you are aware, your team has been briefed by OMB, as well as the relevant agencies, on Operation Warp Speed and other COVID ­relief efforts, including the various funding streams in use for these efforts.

"Furthermore, there is record of your team accessing these critical documents just last week. As the record shows, OMB has fully participated in appropriate transition efforts."

He added: "What we have not done and will not do is use current OMB staff to write the BTT's legislative policy proposals to dismantle this administration's work. OMB staff are working on this administration's policies and will do so until this administration's final day in office. Redirecting staff and resources to draft your team's budget proposals is not an OMB transition responsibility.

"Our system of government has one president and one administration at a time. OMB will not participate in developing policies that will weaken border security, dismantle the president's deregulatory successes, and draft budgets that will bankrupt America," the letter concluded.

But experts on the federal budget say Vought's refusal to give Biden's team access to career OMB officials is unprecedented and could hurt Biden's efforts to roll out big-picture, forward-looking ideas on everything from healthcare to climate change to taxes at the start of his four-year term.

The career OMB staff could provide Biden's team information such as cost estimates and details on existing programs.

Vought said in a series of tweets and in a letter sent to former Sen. Ted Kaufman, Biden's transition leader, that claims his agency has not been cooperative are false.

Biden complained Monday that Trump administration officials at OMB and the Pentagon were hampering his transition, but he did not detail specifics. The people familiar with Vought's actions asked not to be identified because the discussions were private.

"Right now we just aren't getting all the information that we need from the outgoing administration in key national security areas," Biden said after a meeting with his national security advisers and transition officials. "It's nothing short, in my view, of irresponsibility."

No administration from either party has ever prevented its successor from meeting with OMB staff, said William Hoagland, a former top Republican Senate aide who worked on budget policy and appropriations for more than 25 years.

"Not having access to OMB and preparing their budget will further delay any actions they want to pursue. There will be a serious delay in the incoming Biden administration's ability to put forward their budget," Hoagland said in an interview.

The Biden camp has said OMB's alleged stonewalling has particularly set back the president-elect's effort to plan his response to the pandemic.

"OMB's refusal to cooperate impairs our ability to identify opportunities to maximize the relief going out to Americans during the pandemic, and it leaves us in the dark as it relates to Covid expenditures and other gaps," said Yohannes Abraham, executive director of the Biden transition team.

Incoming presidential administrations typically begin their budget planning well before the new president is inaugurated Jan. 20, in order to be able to send the document to Congress relatively soon thereafter. Congress decides how the government spends money, not the president, but the president's budget is an annual statement of his priorities and is a vital source of information on the government's activities.

The annual document is due to Congress on the first Monday in February, but in recent years has often been delayed.

Trump submitted his first budget to Congress about four months after he took office, May 23, 2017. President Barack Obama submitted an initial budget proposal about one month after he took office, Feb. 26, 2009, and provided additional detail in May.