A key review of T-Mobile US and Sprint’s proposed mega merger was once again paused this week, as the US Federal Communications Commission (FCC) halted non-essential operations as part of a broader government shutdown.

In a public notice, the commission said it would suspend its 180-day review process for pending transactions for the duration of the federal closure. Review clocks will restart on the business day following the resumption of normal operations, it added.

The news represents a second delay for the FCC’s review of T-Mobile and Sprint’s merger. It previously halted its evaluation in September to sift through additional documentation submitted by the operators. Consideration of the deal resumed on 4 December, at day 55 of the review timeline.

In November, T-Mobile CFO Braxton Carter suggested the transaction could close as soon as Q1 2019, though conceded a conclusion in Q2 was “more probable”.

The deal received a nod from a number of regulatory bodies, but key permissions from the FCC and the US Department of Justice remain outstanding.

Sprint declined to comment on the shutdown’s impact on the merger’s close date; T-Mobile did not respond to a request for comment.

Laura Phillips, a partner at law firm Drinker, Biddle and Reath who specialises in telecom issues, said in addition to extending the review process for major transactions like the merger, the shutdown will also “have a very immediate impact” on companies and projects which rely on FCC licensing.

“If the shutdown is extended, the backlog on licensing is going to really be an issue for some,” she said. “It creates issues for the communications industry and the broader communications ecosystem, particularly when normal licensing and authorisation processes are not occurring, and there is a backup created from these processes being halted for an unknown period of time.”

The FCC closure comes amid a dispute among US politicians over the allocation of funds to run government agencies, including the FCC. It is unclear how long the shutdown will last; the longest stalemate lasted 21 days between December 1995 and January 1996.

The current closure began for most agencies on 22 December, though the FCC only ran out of cash on Thursday (3 January).