WASHINGTON — As questions mount over President Donald Trump’s tough talk on Iran, top national security officials headed to Capitol Hill Tuesday to brief Congress. But skeptical Democrats sought out a second opinion, holding their own briefing with former Obama administration officials.

The competing closed-door sessions Tuesday, unusual and potentially polarizing, come after weeks of escalating tensions in the Persian Gulf that have raised alarms over a possible military confrontation with Iran. Lawmakers are warning the Trump administration it cannot take the country into war without approval from Congress, and the back-to-back briefings show the wariness among Democrats, and some Republicans, over the White House’s sudden policy shifts in the Middle East.

Trump, veering between bombast and conciliation in his quest to contain Iran, threatened Monday to meet provocations by Iran with “great force,” but also said he’s willing to negotiate.

Before Tuesday’s hearing, Secretary of State Mike Pompeo tweeted that he would “explain the prudent steps we’re taking to deter violence, protect American interests and support the brave Iranian people.” And Defense Secretary Patrick Shanahan suggested the U.S. military response to Iranian threats has already had an effect.

Shanahan said military moves by the United States have given Iran “time to recalculate” and as a result the potential for attacks on Americans is “on hold.”

He cautioned that that doesn’t mean the threats have gone away.

The U.S. sent an aircraft carrier strike group, four bomber aircraft and other assets to the region, and is moving a Patriot missile battery to an unnamed country in the area. The Trump administration has evacuated non-essential personnel from Iraq, amid unspecified threats the administration says are linked to Iran.

Trump inconsistencies have “multiplied the risks” from Iran, according to House intelligence committee Chairman Adam Schiff, who spoke to reporters after Democrats received a closed-door briefing from former CIA Director John Brennan and former State Department official Wendy Sherman, who negotiated the Iran nuclear deal.

Brennan told House Democrats Iran believes Trump wants regime change and while Tehran wants to avoid conflict, the country’s leadership will not capitulate to Trump. Sherman warned that reckless behavior by the Trump administration in Iran is hurting credibility and undermining moderates in the country, according to a person in the room who was not authorized to discuss the private meeting.

House Democrats invited Brennan and Sherman after the administration announced Secretary of State Pompeo, Shanahan and other top brass, including Gen. Joseph Dunford, the chairman of the Joint Chiefs of staff, would appear for closed-door briefings Tuesday afternoon with both the House and Senate.

Schiff declined to comment on what was said in the meeting with Brennan. The California Democrat said he has received the key intelligence assessments, but he still has questions for the Trump administration on Iran.