'This is not the time to show weakness': Trump fights back against senators attempting to limit his powers on war with Iran

Eager to avoid losing an ounce of power, Donald Trump used two tweets to pressure additional Senate Republicans from supporting a measure that would limit his authority to launch military operations against Iran.

A final vote is expected on Thursday on a measure pushed by Democratic Senator Tim Kaine of Virginia that would require the president push through both chambers a formal declaration of war or other "specific" measure giving Congress' blessing for military operations against Tehran.

"The resolution underscores that Congress has the sole power to declare war, as laid out in the Constitution," Mr Kaine said in a statement. "The resolution will force a public debate and vote in Congress as intended by the framers of the Constitution to determine whether United States forces should be engaged in these hostilities."

Mr Kaine, a member of the chamber's Foreign Relations Committee, crafted his measure after Mr Trump ordered the killing of Maj Gen Qassem Soleimani, head of the Iranian Revolutionary Guard's Quds Force. The Trump administration has deemed the IRG a terrorist organisation.

The White House used that designation and the office of the president's Article II powers to defend the country against all threats as legal justification for taking out the Quds leader, backed by most Republicans on Capitol Hill.

Senate Majority Leader Mitch McConnell has voiced his opposition to the Kaine measure, which he deemed "deeply flawed on a number of levels," a signal to his caucus that he wants it to fail.

"It is too blunt and too broad. It is also an abuse of the War Powers Act, which was designed to strike a balance between the president's constitutional war powers and Congress' own war powers and oversight responsibilities," the Kentucky Republican said. "Some of us believe the War Powers Act went too far in undermining the Separation of Powers and infringing upon the authorities of the commander in chief."

The measure has the support of several Senate Republicans – Republican Senators Susan Collins of Maine, Todd Young of Indiana, Mike Lee of Utah, Rand Paul of Kentucky and Jerry Moran of Kansas. But despite those GOP members' support, Mr McConnell is expected to keep enough of his 53 members in line to deny Mr Kaine a two-thirds majority needed to overturn Mr Trump's inevitable veto.

Still, their support has the commander in chief's attention.

"It is very important for our Country's SECURITY that the United States Senate not vote for the Iran War Powers Resolution. We are doing very well with Iran and this is not the time to show weakness. Americans overwhelmingly support our attack on terrorist Soleimani...." Mr Trump tweeted ahead of a procedural vote on the measure. "...If my hands were tied, Iran would have a field day. Sends a very bad signal. The Democrats are only doing this as an attempt to embarrass the Republican Party. Don't let it happen!"

All post-9/11 American presidents have been sceptical of – or outright opposed to – various measures floated over the years that would have harnessed the powers of their office to wage war or conduct one-off military strikes on violent extremist groups. Mr Trump's opposition to the Kaine measure is one of the handful of similarities he has with George W Bush and Barack Obama – both of whom, like Mr Trump, used Article II and a purposely legally broad authorisation for the use of military force to justify all kinds of military and other operations against terrorist organisations or their associated forces.