(CNN) Republican Sen. Jim Risch of Idaho, who chairs the powerful Senate Foreign Relations Committee, has been briefed by the Trump administration about the escalating tensions with Iran .

But Democratic Rep. Eliot Engel of New York, the chairman of the equally powerful House Foreign Affairs Committee, had not as of Thursday afternoon.

Sen. Mitt Romney of Utah, a freshman Republican who chairs a subcommittee of the Foreign Relations Committee, was briefed on the Iran situation about a week ago.

But Sen. Lindsey Graham of South Carolina -- a veteran GOPer who sits on that same committee and chairs an appropriations subcommittee that oversees funding for the State Department -- has not had his calls returned on the matter.

As the Trump administration unevenly briefs some members -- but not others -- about a roiling situation that could lead the US into military conflict, some who are in the dark are left fuming.

"I think they should tell us what the hell is going on," Graham told CNN. "I'm tired of being asked questions, which is your job -- I'm not mad at y'all guys. I don't know what to tell you."

And after briefing the GOP-led Senate Intelligence Committee, the Trump administration abruptly scrapped a briefing with the House Intelligence Committee, led by Democrats.

"We did have a full committee briefing that was canceled," Schiff told CNN. "That concerns me greatly. ... Members need to be brought into what our intelligence agencies know."

What has infuriated some members is that they have learned key details from reporters -- and not the administration -- most notably about the removal of US personnel from the embassy in Baghdad and consulate in Erbil, Iraq. Graham and his Democratic counterpart on the appropriations subcommittee, Patrick Leahy of Vermont, fired off a letter to Secretary of State Mike Pomelo saying they have "great concern" about the news they read of the evacuation, demanding a briefing as soon as possible.

"It's a major deal to move people out of a consulate in Iraq. They were there during the war," Graham said in the Capitol. "I'm not doubting it's a real threat. I'm just frustrated they can't pick up a phone and tell us -- particularly me and Sen. Leahy, because we are in charge of embassy and consulate security. This is a mistake."

Some Democrats are questioning why top Republicans seem more likely to get briefed -- rather than Democrats.

Sen. Bob Menendez, the top Democrat on Senate Foreign Relations, said he's concerned there's a "disparity" in the way the administration is treating Democrats versus Republicans.

"We all have one vote. We all have to make critical decisions based on that information," said Menendez of New Jersey on Thursday. "I'm concerned about one not being able to get it."

The State Department did not respond to a CNN request for comment for this story.

The Trump administration has started to take steps to brief more members of Congress. On Thursday, senior administration officials, including Director of National Intelligence Dan Coats, briefed the so-called Gang of Eight, the top leaders of Congress and the House and Senate intelligence panels from both parties. The administration has also allowed senators to begin to review some of the classified intelligence at a secure location on Capitol grounds.

Leaving the Gang of Eight briefing, Sen. Mark Warner, who serves as vice chairman of the Senate Intelligence Committee, said it was "an important first step. The Virginia Democrat added: "I hope that with appropriate restraints more members hear the whole story."

Yet Schiff, who was part of the Gang of Eight briefing, raised significant concerns, saying afterward that the administration lacks a "sound policy" on Iran.

"It appears we may be putting ourselves in a position that makes us far less safe, not more," Schiff told CNN Thursday night.

Indeed, more briefings are expected with the full Senate and House next week -- but it's unclear how much new information the lawmakers will get and who will do the briefing.

"I'm not yet satisfied," said Sen. Todd Young of Indiana, a GOP member of Senate Foreign Relations. "But I anticipate being satisfied in the very near term based on some meetings that were set."

The Trump administration has briefed some key committees, including the Senate Intelligence Committee, a panel of which Risch is a member. But Risch got his briefing in his capacity as chairman of Senate Foreign Relations, according to a Risch spokesperson, even though Engel, his House counterpart, has not.

Engel "has not" been briefed, according to a committee aide. "And he's not pleased by that."

Engel himself added: "I think that Congress should have been briefed about it so that we didn't have to read about it in newspaper and television accounts, and I think the administration should give us a classified briefing as soon as possible."

"We have asked for a briefing," added Sen. Jack Reed of Rhode Island, the top Democrat on the Senate Armed Services Committee. "This should be a situation where they engage Congress early -- on both sides of the aisle."

But some Democrats have received some information -- including Sen. Chris Murphy of Connecticut, who is the ranking member on the Foreign Relations subcommittee that Romney chairs. Murphy said he took part in a separate briefing from Romney -- but he said it's unclear if the information he was told amounted to the full picture of the state of play with Iran.

"Right now, it's my sense ... it is totally ad hoc," Murphy said of the briefings. "There have been some proactive briefings for Republicans. My sense as a Democrat (is) you can seek it out. ... But nobody is giving it out willingly."

Sen. Tim Kaine, a Virginia Democrat on the Senate Foreign Relations and Armed Services committees, said he'd had "some conversations" at the classified level regarding the current US posture toward Iran, but still had significant questions.

"I still think there's a real issue about the US attempting to provoke stuff," Kaine told CNN. "I think the Trump administration would like Americans to believe that it's Iran acting, or potentially acting, unilaterally against us, but I think the US is trying to provoke them."

Romney said his private briefing was a "week or so ago" and that "no one is looking to go to war."

"No one wants to go to war in the Middle East," Romney told CNN. "We've tried it before -- it didn't work out so well."