WASHINGTON ― Calls are mounting on Capitol Hill to block moves by President Donald Trump that are related to potential hostilities with Iran, arms sales to Saudi Arabia and the war in Yemen.

The bipartisan frustration is focused on the Republican president’s invocation of emergency powers to bypass congressional review of $8.1 billion in weapon sales for Saudi Arabia, Jordan and the United Arab Emirates.

In a statement Tuesday, the House’s powerful No. 2 Democrat, Rep. Steny Hoyer, condemned the administration’s “blatant violation of our system of checks and balances” for bypassing Congress’ long-standing role in approving or blocking arms sales to foreign militaries.

Hoyer vowed to "ensure that Congress asserts its proper role over arms sales” by working with House Armed Services Committee Chairman Adam Smith, D-Wash., and House Foreign Affairs Committee Chairman Eliot Engel, D-N.Y. Hoyer did not offer specifics.

Rep. Ro Khanna, D-Calif., expressed hope Wednesday the president’s action would spur House Speaker Nancy Pelosi, D-N.Y., to pursue a court challenge of Trump’s veto of a measure to end U.S. military aid to Saudi Arabia in Yemen. (Vox reported Tuesday that Khanna was among lawmakers and legal scholars who want Pelosi to sue Trump in the Supreme Court over U.S. involvement in Yemen.)

“I’m confident these new arms sales provides new momentum for pursuing legal action and legislation that would end U.S. involvement in the war,” Khanna tweeted Wednesday. “With constitutional precedent on our side, I hope the Speaker and the House ... will pursue legal action because we must reassert our war powers jurisdiction, especially in the face of these new actions by the president to circumvent Congress.”

Since Trump vetoed a war powers resolution in April that would have directed him to remove U.S. troops from “hostilities” in Yemen, he has sent 1,000 additional troops to the Mideast to counter Iran and bypassed Congress on the sales to Riyadh and its allies. The Senate in May failed to override Trump’s veto.

On Friday, the Defense Security Cooperation Agency announced seven sales to the region, in part including two aircraft follow-on support and services to Saudi Arabia worth more than $2 billion, as well as RQ-21A Blackjack drones and Javelin missiles to the UAE. Further sales are expected to be announced in the Federal Register this week.

The Arms Export Control Act contains an exemption to sell weapons to partners in case of an emergency, something designed to speed up the process amid a crisis. In this case, Trump appears to be using the tense situation with Iran — based on intelligence reports that have been widely questioned by Democrats, but supported by the Pentagon — as a reason to push through the weapons.

Even some Republicans are vexed.

“I understand the administration’s frustration that key members of Congress held these arms sales for an extended period of time, in some cases for over a year,” Rep. Michael McCaul, R-Texas, the House Foreign Affairs Committee’s ranking member, said in a statement after the notification. “However, the president’s decision to use an emergency waiver on these sales is unfortunate and will damage certain future congressional interactions.”

In the Senate, several Democrats including Senate Foreign Relations Committee ranking member Bob Menendez, D-N.J.; Chris Murphy, D-Conn.; and senior appropriator Chris Van Hollen, D-Md., are considering an amendment to the U.S. State Department’s appropriations bill aimed at barring the arms sales.

“This Administration’s decision to bypass Congress and sell arms to Saudi Arabia is a misapplication of this provision and an abuse of power,” Van Hollen said in a statement Friday. “I will work to close this loophole in the appropriations process and use every available tool to prevent President Trump from taking this action.”

The chairman of the subcommittee with jurisdiction over State Department appropriations, South Carolina Republican Sen. Lindsey Graham, is the co-sponsor of the Saudi Arabia Accountability and Yemen Act, which bars certain U.S. weapons sales to Riyadh. (Menendez is one of the co-sponsors of that legislation.)

“I don’t support the arms sales now, but I do support American troops going into the Mideast in larger numbers to deter Iran,” Graham told Fox News on Sunday, citing his belief Saudi Crown Prince Mohammed bin Salman ordered the killing of journalist Jamal Khashoggi.

Sen. Tim Kaine, D-Va., said he hopes to force a vote on Trump’s authority for a war with Iran during the upper chamber’s floor debate of the 2020 defense authorization bill, likely in the coming weeks. He has an amendment meant to prevent funding for any military action against Iran except in self-defense, or if Congress approves a separate war authorization, he said in a call with reporters last week.

Kaine would be betting that at least some Republicans are willing to buck the president on matters of war, as they did in March when the the Senate voted 54-46 to pass the war powers resolution on Yemen. Still, what amendments make it to the floor typically depend on decisions made behind closed doors between GOP and Democratic leaders.

When Kaine tried to bring up the amendment in the Senate Armed Services Committee’s closed markup of the defense authorization bill, the GOP chairmen of the Senate Armed Services and Foreign Relations committees scuttled it there for jurisdictional reasons. Kaine sits on both committees.

“That we would not be able to discuss all of these issues about potential war with Iran in the Armed Services Committee, it’s like the scene in 'Dr. Strangelove’ where the president says no fighting in the war room,” Kaine said. “Are you kidding? This is exactly the place we should be having this discussion.”