Vaccine rations constraints are hindering the Trump administration’s beliefs of striking a deal with Pfizer to buy extra 100 million doses of the firm’s coronavirus vaccines, the newest impediment to ramping up vaccine creation as the virus quickly spreads. Executives from the Trump administration and Pfizer validated that the two sides are settling for the government to acquire the extra doses for delivery between April and June 2021. But the timing has been a sticking point, as the US clamors for delivery as soon as possible while Pfizer balances the global market.

Health and Human Services Secretary Alex Azar announced Wednesday that a complicating part in the discussions is that Pfizer is having some supply chain problems that will make it more difficult for the company to generate 100 million more doses in the spring season. The federal government is consulting with Pfizer to see how it can assist with those manufacturing issues to get the extra 100 million doses. He said that they were involved in active negotiations with Pfizer about exercising options under their contract, Azar announced during an Operation Warp Speed news briefing that they’ve been working with them on what support is suitable to ensure extra doses.