In a formal statement released by the White House, Trump called the measure a "very insulting resolution" that Democrats introduced as a wedge issue to divide Republicans ahead of the November elections.
The Constitution gives Congress the sole power to declare war.
The president insisted that the U.S.is not now "engaged in the use of force against Iran" and said his January assassination of Iranian Gen. Qasem Soleimani with a drone strike in Baghdad was "fully authorized by law"-a claim legal experts have disputed".
Iran responded by launching ballistic missiles at an Iraqi base housing U.S troops that left more than 100 soldiers injured with traumatic brain injuries.
"The U.S. and Iran are still a spark away from conflagration", said Abdi.
The move marks the seventh time Trump has used his veto pen, including on a previous war powers resolution related to the U.S. military's assistance to Saudi Arabia in Yemen's civil war.
Congress, get this deal done
The PPP, which launched April 3, is meant to help small businesses with fewer than 500 employees stay afloat. President Trump urged the House to pass the deal quickly so he can sign it into law this week.
Aides to Senate Majority Leader Mitch McConnell, R-Ky., did not immediately respond to a request for comment on when the chamber would hold an override vote, which is nearly certain not to meet the two-thirds threshold to successfully overturn a veto.
The resolution, Trump said in a statement, "would have greatly harmed the President's ability to protect the United States, its allies, and its partners". "The resolution implies that the President's constitutional authority to use military force is limited to defense of the United States and its forces against imminent attack". But the actual transmission of the congressional resolution to the White House was delayed for almost two months as Congress left Washington due to the coronavirus pandemic, according to aides. "Congress should seek to pass this resolution again and overcome the presidential veto, whether by overriding or inserting war prohibitions into a must-pass bill later this year". "That starts today with upholding the president's rightful veto of a misguided war powers resolution".
Trump did not consult with congressional leaders ahead of the attack on Soleimani, and there was concern in Congress that Tehran and Washington were perilously close to all-out conflict. None of Trump's vetoes have been overridden.
It is the second time Mr. Trump has vetoed an attempt by Congress to control his military initiatives.
"I urge my colleagues to join me in voting to override his veto".
The administration has argued that killing Iranian Gen. Qassem Suleimani was necessary to prevent imminent attacks on Americans. Congress made clear that it has never authorised the President to use military force against Iran.
Trump insisted that the strike "was fully authorized by law, including the Authorization for Use of Military Force against Iraq Resolution of 2002 and Article II of the Constitution".