Senate Minority Leader Chuck Schumer has voiced concerns ahead of a high-stakes, closed-door US Secretary of State Rubio’s briefing to the Congressional leaders.
"Look, this is serious," he told reporters on Tuesday.
"If the administration wants to do something in Iran, and who the hell knows what it is, they should make it public and discuss it with the public, and not keep it in secret."
Schumer has insisted that the Trump administration must "make its case to the American people" before moving forward with any military escalation.
He has warned that conducting operations in the shadows often leads to disaster, stating: "When you do these military operations in secret, it always causes longer wars, tragedy, more expenses and mistake."
Crucial meeting
The session, led by Rubio and attended by CIA Director John Ratcliffe, has brought together the "Gang of Eight" — senior leadership from both chambers and their respective intelligence committees.
The briefing is slated to take place as the Trump administration considers possible military attacks on Tehran.
House Minority Leader Hakeem Jeffries has mirrored Schumer’s concerns, warning against unilateral action.
"American people understand that under no circumstances should the Trump administration get us into another failed foreign forever war," Jeffries has said, adding that such action would "cost American lives" without leading to "any decisive resolution."
Jeffries has also challenged the administration's credibility, pointing to US President Donald Trump's previous claim that strikes had already "completely and totally obliterated" Tehran's nuclear capabilities.
"Wait, what happened to Iran's nuclear programme being completely and totally obliterated? Donald Trump's words, not our words," Jeffries said, questioning why there is now a new sense of "exigent circumstance."
The briefing comes as tensions have risen dramatically following the deployment of US aircraft carriers and over 120 military aircraft to the Middle East.
A third round of indirect nuclear talks, brokered by Oman, is due to begin in Geneva on Thursday, representing a final window for diplomacy.
Iran says a deal to avoid a military clash with the US is within reach, but has repeatedly warned it would respond firmly to any attack.
