Frustrated by Senate Republicans' inability to advance legislation, President Trump on Tuesday called for an end to the 60-vote threshold that is needed to break a filibuster in the upper chamber.

"We have to get rid of what's called the filibuster rule. We have to," Trump told the thousands of supporters who braved the heat to attend his rally in Phoenix. "If we don't, the Republicans will never get anything passed."

He continued, "We have to get rid of the filibuster rule right now. We have 60 votes and we have 52 Republicans. That means that eight Democrats are controlling all of this legislation."

The president's renewed call for a major change to Senate rules comes weeks after the GOP effort to repeal and replace Obamacare collapsed in the upper chamber due to a lack of support for several measures. Only 49 Republicans voted for the so-called "skinny repeal" bill that finally sunk the party's push for healthcare reform. But some regulatory changes that might have won Republican votes could not be advanced through the reconciliation process being used to avoid filibusters.

Senate Majority Leader Mitch McConnell, R-Ky., previously rejected such a move, telling reporters in May that eliminating the filibuster "would fundamentally change the way the Senate has worked for a very long time."

"We're not going to do that," McConnell had said.

Senate Republicans have already attempted to bypass the rule via reconciliation, which requires a simple majority of 51 votes – including a tie-breaking vote by Vice President Mike Pence – to pass any legislation that impacts the budget.

Republicans hope their upcoming bid for comprehensive tax reform will succeed, despite their recent failure to pass a healthcare bill using the reconciliation measure.