Since disclosing an alleged Iranian assassination plot on Tuesday, the Obama administration has offered tough rhetoric when it comes to holding Tehran accountable. Officials have also announced a handful of new sanctions.

On Capitol Hill, they’re not impressed.

Indeed, some of the most heated language on Iran has been coming from lawmakers. And while the toughest response has been from Republicans, Democrats also have been expressing growing impatience with the administration’s policy of trying to engage Iran through a series of carrots and sticks.

“On October 11th, 2011, the United States approach to the Iranian regime should have undergone a major change,” Rep. Ileana Ros-Lehtinen (R-Fla.), chairman of the House Foreign Relations Committee, said at a hearing on Friday. Yet “the administration does not plan to alter its course of pressure and persuasive engagement with the Iranian regime.”

“Let me be blunt,” Ros-Lehtinen added. “This planned murder-for-hire must serve as a wakeup call regarding the determination and capability of the Iranian regime.”

Earlier this week, Rep. Peter King (R-N.Y.) called the Iranians’ alleged scheme to kill the Saudi ambassador to Washington “an act of war” against the United States and Saudi Arabia. Sen. Carl Levin (D-Mich.), when asked whether he agreed with the assessment, said, “It may be,” then added that he would “want to see ... the implications” before coming to such a conclusion.

For years, the Obama administration — and the Bush administration before it — has tried to press Iran to relinquish its nuclear ambitions, renounce terrorism and take some sincere steps toward engagement. The strategy has involved a combination of economic and political incentives on the one hand and economic sanctions and diplomatic pressure on the other.

Since the disruption of the murder-for-hire plot, there have been more sticks. The Obama administration imposed sanctions on a handful of Iranian officials and on an Iranian commercial airliner accused of “secretly ferrying operatives, weapons and funds” on behalf of the Islamic Revolutionary Guard Corps’ Quds Force, which was implicated in the plot.

As Wendy Sherman, undersecretary for political affairs at the State Department, told Ros-Lehtinen’s panel, the Obama administration now has the toughest sanctions package on the Islamic Republic in three decades.

There are calls for more sanctions, including against top Iranian officials and entities not yet targeted and against the Central Bank of Iran.

But beyond the sanctions, there are growing questions about whether the administration needs to take an even bolder strategy — more sticks and fewer carrots.

The problem is, with little talk of military action or a blockade on Iran’s oil industry, it’s unclear what that strategy might be.

What is clear to many lawmakers is that increasing pressure on Iran through sanctions, even when done in coordination with international allies, may never produce meaningful change.

“You know, it sounds like more and more carrots to Iran, to me,” Rep. Steve Chabot (R-Ohio) said at Friday’s hearing. “It seems to be painfully obvious that our policy not only remains unchanged, but that it has failed to achieve our core objective.”