Imran Khan reiterated Pakistan's full support and solidarity with the brotherly country against any threat to its security and territorial integrity.
Two sources briefed on state oil company Saudi Aramco's operations told Reuters it might take months for Saudi oil production to return to normal.
There was a sharp uptick in tensions between Washington and Tehran when Trump previous year pulled the United States out of a landmark agreement between world powers and Iran in which Tehran accepted curbs on its nuclear program in exchange for relief from global sanctions.
The worst ever sudden disruption to global oil supplies continues to reverberate as geopolitical risk premiums jump on concern over instability in the Middle East and a potential retaliation against Iran, which the US has blamed for the strikes.
Separately, other US officials say the evidence that already has been collected is conclusive and points directly to Iran.
The officials did not provide evidence or explain what USA intelligence they were using for the evaluations. It has also created a pressure-packed situation in the Middle East, where a proxy war in Yemen between Iran and its Saudi rivals now threatens to escalate into a regional conflict.
The prospect that the United States and other industrialised countries could release oil from their strategic reserves has weighed on prices.
Earlier in the day, Saudi Aramco had allowed its employees to re-enter the Abqaiq oil-processing facility for the first time since Saturday's attacks. But U.S. officials say the available evidence is showing that is not possible.
Iranian-allied Houthi rebels in Yemen, which Saudi Arabia are at war with, claimed responsibility, saying drones were launched in the attack.
While Washington has cast blame on Tehran, Yemen's Houthi rebels claimed responsibility for this weekend's strikes, which devastated a pair of Saudi oil treatment facilities and disrupted almost five percent of the global oil market, or 5.7 million barrels per day.
Fears Saturday's strikes would hit global supplies sent prices 20% higher.
The Persian Gulf region has witnessed greater unrest since Trump's decision past year to abandon a 2015 nuclear deal with Iran.
The Houthis have launched attacks on oil fields in Saudi Arabia before, but this weekend's strikes were more sophisticated than past assaults.
"We're locked and loaded and we're ready to defend our interests and allies in the region, make no mistake about it", he said, echoing President Donald Trump's words on Monday.