Joe Biden, the US president-elect, complained on Monday that his national security team has run into “obstruction” and “roadblocks” from political leadership at the Pentagon. The criticism came after the defence department earlier this month suddenly suspended briefings with the Biden transition team, and with Donald Trump still seeking to overturn his election defeat. “From some agencies, our team received exemplary cooperation,” Biden said in Wilmington, Delaware, after a briefing by his foreign policy advisers. “From others, most notably the Department of Defense, we encountered obstruction from the political leadership of that department.” Both the defence department and Office of Management and Budget erected “roadblocks”, he added. “Right now we just aren’t getting all of the information that we need from the outgoing administration in key national security areas. It’s nothing short, in my view, of irresponsibility.” The president-elect, who takes office on 20 January, warned that his team needs “full visibility” into the budget process at the Pentagon “in order to avoid any window of confusion or catch-up that our adversaries may try to exploit”. The remarks were the latest sign of Biden’s increased willingness to take off the gloves in condemning Trump’s reluctance to take part in a swift and orderly transition. The current president has still not invited his successor to the White House or confirmed his attendance at the inauguration, as is traditional. Trump fired his defence secretary Mark Esper after the 3 November election, replacing him with Christopher Miller in an acting capacity. Earlier this month, Biden’s team complained about an abrupt halt in cooperation from the Pentagon. The defence department claimed that meetings had been postponed until January because of a “mutually agreed upon” pause but the transition team insisted that there is no such agreement. The team also said they had met resistance to requests for information from some Pentagon officials. But a senior defence official told the Reuters news agency that the Pentagon had conducted 163 interviews and 181 requests for information and that it would continue to provide information and meetings. Trump has refused to acknowledge Biden’s victory, claiming widespread voter fraud for which there is no evidence and suffering dozens of court defeats. His administration only authorised cooperation with Biden on 23 November. Trump has vowed to make a last stand on 6 January when Congress convenes to certify the electoral college results. Jenna Ellis, a member of his legal team, tweeted on Monday: “President Trump should never concede the election.” Biden was briefed on Monday by his nominees for secretary of state, defence and homeland security, as well as his incoming national security adviser. He said his team found that agencies “critical to our security have incurred enormous damage” during Trump’s tenure. “Many of them have been hollowed out in personnel, capacity and in morale. There’s policy processes that have atrophied or have been sidelined to the disrepair of our alliances. It makes it harder for our government to protect the American people.” Biden’s foreign policy team has been described as a return to experience, expertise and the Barack Obama era, with Tony Blinken nominated for secretary of state, Jake Sullivan for national security adviser and John Kerry in a new role as special presidential envoy for climate. Lloyd Austin is facing a confirmation battle as defence secretary because he is a retired general, potentially undermining the principle of civilian control of the military.