Iran is vowing on Monday to "use all available tools" in response to Israel’s strategic airstrikes against the country despite a warning from the Israel Defense Forces (IDF) to stand down or pay a "heavy price." 

"[Iran] will use all available tools to deliver a definite and effective response to the Zionist regime," Iranian Foreign Ministry spokesperson Esmaeil Baghaei declared during a televised news conference, according to Reuters. 

Israeli air force jets struck 20 targets across Iran early Saturday during the operation, named "Days of Repentance." The operation unfolded with an initial assault on Iran’s air defense systems, followed by targeted strikes by more than 100 airplanes on missile and drone bases and weapons production sites.  

The IDF then announced later in the day that it is prepared to target Iran again if it responds to the strikes. 

ISRAEL’S ‘DAYS OF REPENTANCE’ STRIKES AGAINST IRAN WILL CONTINUE IF TERROR REGIME RESPONDS, IDF WARNS 

"If the regime in Iran were to make the mistake of beginning a new round of escalation -- we will be obligated to respond. Our message is clear: All those who threaten the State of Israel and seek to drag the region into a wider escalation -- will pay a heavy price," IDF spokesperson Rear Adm. Daniel Hagari said. 

"We demonstrated today that we have both the capability and the resolve to act decisively -- and we are prepared -- on offense and defense -- to defend the State of Israel and the people of Israel," Hagari added. 

ISRAEL’S TARGETED RESPONSE AGAINST IRAN SENDS NEW WARNINGS TO REGIME ABOUT IDF’S CAPABILITIES, EXPERTS SAY 

President Biden told reporters Saturday that he met with intelligence community officials following the Israeli strikes and that "my hope is this is the end." 

"We maintain the importance of supporting Israel’s right to defend itself," Vice President Kamala Harris also said following the strikes. "We are also very adamant that we must see de-escalation in the region going forward, and that will be our focus." 

Fox News’ Benjamin Weinthal and Efrat Lachter contributed to this report.