In an agreement that he called "a long time coming," President Obama announced that the U.S., Iran and other countries have reached a historic framework to curb Iran's nuclear program. (AP)

This story has been updated.

President Obama on Thursday announced a potentially historic nuclear agreement with the Islamic Republic of Iran, the culmination of intense negotiations between the United States, Iran and several world powers.

Speaking from the Rose Garden, Obama stressed that the deal -- which none of the parties involved have yet formally agreed to -- represented the best possible path to prevent Iran from acquiring a nuclear weapon.

“Sanctions alone could not stop Iran's nuclear program, but they did help bring Iran to the negotiating table. Because of our diplomatic efforts, the world stood with us,” Obama said. “Today, after many months of tough principle diplomacy, we have achieved the framework for that deal.

"And it is a good deal, a deal that meets our core objectives," the president added.

[Fact sheet from State Department: Parameters of plan on Iran nuclear program]

As part of the unprecedented framework, the Iranian government has agreed not to stockpile materials it could use to build a nuclear weapon. In exchange, the United States and several world powers have agreed to provide Iran with relief from certain sanctions placed on it by the international community.

The president said that sanctions placed on Iran "for its support of terrorism, its human rights abuses, its ballistic missile program" will remain in place.

Secretary of State John Kerry, speaking from Lausanne, Switzerland, said that the final agreement "will not rely on promises, it will rely on proof," saying that diplomatic relations moving forward will depend on Iran's compliance with the terms of the agreement.

Both the president and Kerry stressed that Iran will be under close scrutiny moving forward.

"If Iran cheats, the world will know it. If we see something suspicious, we will inspect it," Obama said. "With this deal, Iran will face more inspections than any other country in the world. So, this will be a long-term deal that addresses each path to a potential Iranian nuclear bomb."

President Obama has made the negotiations between Iran, six major world powers and the European Union a centerpiece of his foreign policy, investing any final outcome with major potential benefits and risks.

The pact came after an all-night work session that extended well past the talks' original deadline of March 31. State Department spokeswoman Marie Harf tweeted Thursday afternoon, "For those keeping track, it's 6am in Lausanne. That was truly an all-nighter."

Negotiators from Iran and major world powers reached agreement on a framework for a final agreement to curb Tehran's nuclear program in exchange for relief from international sanctions, participants in the talks said. (Yahoo News)

Obama had been slated to leave early Thursday afternoon to deliver an economic speech in Louisville, but remained in the White House as the deal in Lausanne, Switzerland coalesced.

Iranian President Hassan Rouhani tweeted just before 1 p.m. ET, "Solutions on key parameters of Iran case reached. Drafting to start immediately, to finish by June 30th."

Before coming out to speak Obama spoke separately with French President Francois Hollande, German Chancellor Angela Merkel and British Prime Minister David Cameron.

According to a statement released by the White House, "The leaders affirmed that while nothing is agreed until everything is agreed, the framework represents significant progress towards a lasting, comprehensive solution that cuts off all of Iran’s pathways to a bomb and verifiably ensures the peaceful nature of Iran’s nuclear program going forward."

The president also called Saudi Arabian King Salman bin Abdul Aziz to discuss the agreement, and phoned Israeli Prime Minister Benjamin Netanyahu while aboard Air Force One Thursday afternoon.

As Obama's motorcade made its way to Joint Base Andrews shortly after the speech large, cheering throngs stood along the route through the Mall and along the Tidal Basin. At 3:21 p.m. the motorcade arrived at Andrews Air Force Base, roughly three hours behind schedule, and the president jogged up the stairs to Air Force One as he prepared to take off on the flight to Kentucky.

 Jose DelReal contributed to this report.