President Donald Trump speaks during an "Evangelicals for Trump Coalition Launch" at King Jesus International Ministry
President Donald Trump and first lady Melania Trump exit Air Force One, Sunday, Jan. 5, 2020, at Andrews Air Force Base, Md., following a trip to his Mar-a-Lago estate.

Huge crowds gathered Monday in Tehran to mourn top general Qassem Soleimani, as his replacement vowed to take revenge for the U.S. airstrike that killed him, and U.S. President Donald Trump threatened to hit Iranian cultural sites if Iran does retaliate.

"They're allowed to kill our people. They're allowed to torture and maim our people. They're allowed to use roadside bombs and blow up our people and we're not allowed to touch their cultural sites? It doesn't work that way," Trump told reporters aboard Air Force One late Sunday.

House to vote on war powers resolution
 

US Speaker of the House Nancy Pelosi speaks alongside a stack of legislation the House has passed as she holds a press conference with fellow Democrats at the US Capitol in Washington, DC, December 19, 2019.

House Speaker Nancy Pelosi said in a letter to her Democratic colleagues that the House will vote this week on a war powers resolution "to limit the President's military actions regarding Iran."

"It reasserts Congress's long-established oversight responsibilities by mandating that if no further Congressional action is taken, the Administration's military hostilities with regard to Iran cease within 30 days," Pelosi wrote.

She called last week's airstrike "provocative and disproportionate," and said it endangered U.S. troops while escalating tensions with Iran.

"We're now headed very close to the precipice of war," Sen. Chris Van Hollen told Fox News, adding "you just can't go around and kill" world figures the U.S. opposes. "The president is not entitled to take us to war" without congressional authorization.

Republicans back Trump
 

FILE - U.S. Senator Lindsey Graham speaks during a press conference

Sen. Lindsey Graham, one of Trump's Republican allies, said the president "did the right thing" and that his national security team is "doing a great job helping President Trump navigate Iranian provocations."

Republican Congressman Mike Johnson also backed Trump, writing on Twitter, "Now we must remain united against Iranian aggression while praying and working for de-escalation."

Trump tweeted Sunday that his social media posts "will serve as notification to the United States Congress that should Iran strike any U.S. person or target, the United States will quickly & fully strike back, & perhaps in a disproportionate manner.  Such legal notice is not required, but is given nevertheless!"

Congressional notification

Yale University law professor Oona Hathaway told VOA the president cannot notify Congress of his intent to go to war by tweet and said he would be breaking several laws.

"Any time the president involves the armed forces into hostilities, he must -- at a minimum -- notify Congress within 48 hours," she said.

The Capitol Hill building is pictured in Washington, DC. (Photo: Diaa Bekheet)

Hathaway added that a president is obligated to consult with Congress before putting the armed forces into any hostilities. She said a "disproportionate" response would break international law, which says any action taken in self-defense must be proportionate to the threat.

European leaders react

The leaders of Britain, France and Germany issued a joint statement Monday citing the urgent need for de-escalation and saying a new crisis in Iraq "risks jeopardizing years of effort" to stabilize the country.

They further called on Iran to "refrain from further violent action or proliferation" and to reverse the steps it has taken away from the 2015 nuclear agreement that constrained its nuclear program in exchange for sanctions relief.

Iran said Sunday it is no longer limiting the number of centrifuges used to enrich uranium, a move that follows earlier actions to ignore limits on the amount of uranium it is allowed to stockpile and how highly it can enrich uranium.

"Iran's nuclear program will have no limitations in production including enrichment capacity and percentage and number of enriched uranium and research and expansion," a government statement said.

Iran did not make any explicit threats to build a nuclear weapon, something it has always denied it wants to do. It also said it will still cooperate with the International Atomic Energy Agency.

Iran's gradual stepping back from the commitments it made under the nuclear deal have come since U.S. President Donald Trump pulled the United States out of the agreement in 2018 and reimposed sanctions on Iran.

Trump also told reporters Sunday he "may discuss" releasing the intelligence he used to justify ordering Soleimani's death.

Secretary of State Mike Pompeo has so far refused to publicly share the evidence supporting the administration's claim that Soleimani was planning imminent attacks on U.S. forces and officials in the Middle East.

FILE - Secretary of State Mike Pompeo delivers remarks at the State Department in Washington, Dec. 19, 2019.

"There are simply things we cannot make public," Pompeo told Fox News. "You've got to protect the sources providing the intelligence."

Trump claimed Soleimani was responsible for the deaths of thousands of Americans, Iraqis and Iranians, saying the longtime Iranian general "made the death of innocent people his sick passion" while helping to run a terror network that reached across the Middle East to Europe and the Americas.

Iraq has filed an official complaint with the United Nations secretary-general and the Security Council over the missile strike against Soleimani, which was carried out on Iraqi soil.