Forty-nine of the 50 Republicans in the Senate have announced they will not back a new nuclear deal between Iran and world powers, underscoring their party’s opposition to attempts to revive a 2015 accord amid fears multilateral nuclear talks might collapse.

Former President Donald Trump withdrew the US from the deal in 2018 and Washington has been enforcing a “maximum pressure” campaign of sanctions against Tehran. In response, Iran has ramped up its nuclear program, including uranium enrichment.