Speaking at a joint press conference, Obama made his administration's stance clear on the position of Assad in a political settlement, underlining that he must depart to pave the way for a solution.
"We're going to keep increasing the pressure on the Assad regime and working with the Syrian opposition," Obama said. "We both agree that Assad needs to go."
Erdoğan says the US and Turkey have overlapping goals when it comes to Syria. Neither leader mentioned that the US and Turkey remain far apart on just how to handle Syria's bloody civil war. Erdoğan did not directly answer a question about what he asked from Obama on Syria.
Obama said the United States can't act alone to bring peace to Syria and needs the cooperation of international partners.
"There's no magic formula for dealing with an extraordinarily violent and difficult situation like Syria," Obama said.
Erdoğan's visit to the US came days after twin car bombings in Hatay's Reyhanlı town along the border with Syria. On Saturday, one of the car bombs exploded outside the city hall while the other went off outside the post office in the town of Reyhanlı, a main hub for Syrian refugees and opposition activity in Turkey's Hatay province. Fifty-one people were killed and as many as 100 were injured in the bombings.
Offering his condolences to victims of the Reyhanlı bombings, Obama said both countries are determined to jointly fight against terrorism in the face of enduring threats.
Praising Turkey's economic success over the past few years, Obama said he will renew efforts to deepen trade ties between the two countries.
During the news conference at rainy Rose Garden, Erdoğan said he intends to go ahead with a planned trip to the Gaza Strip next month despite pressure from the United States to delay it.
"I place a lot of significance on this visit in terms of peace in the Middle East," Erdoğan said, adding that he also plans to visit the West Bank on that trip. He said he hopes his visit will contribute to reconciliation efforts in Palestine.
When asked about the use of chemical weapons in Syria and what an American response would be, Obama said he reserves the right to resort to a range of both diplomatic and military options if he receives conclusive proof that Assad’s government has used chemical weapons in the country's civil war.
Obama said there was evidence of chemical weapons use in Syria but that it is important to get "more specific information" to confirm that before deciding how to respond.
Asked about Turkey's investigation of the use of chemical weapons in Syria, Erdoğan said the Turkish side is sharing any information with allies, not only the US but also others, including the UK.
Erdoğan had been expected to push Obama, at least in private, for more assertive action on Syria during a visit to Washington this week, days after car bombs tore through a Turkish border town in the deadliest spillover of violence yet.
But the two leaders showed no sign of friction in their appearance in the White House Rose Garden and sought to project a united front on Syria.
Obama - who has been reluctant to arm Syrian opposition forces or become enmeshed militarily in the two-year-old conflict - expressed hope that the United States and Russia would succeed in arranging a peace conference that would produce results.
But Obama, who had insisted chemical weapons use would be a "game changer," made clear, however, that Washington was keeping all options on the table, though he did not provide specifics.
"There are a whole range of options that the United States is already engaged in," he told reporters. "And I preserve the options of taking additional steps, both diplomatic and military, because those chemical weapons inside of Syria also threaten our security over the long term as well as our allies and friends and neighbors."
Erdoğan said Turkey was in "full consensus" with the United States on the need to end the bloodshed in Syria and for a political transition to a government without Assad.
Erdoğan expected to meet US officials, businessmen
In addition to Obama, the Turkish prime minister was scheduled to meet with Vice President Joe Biden and Secretary of State John Kerry over lunch and have talks with Speaker of the US House of Representatives John Boehner later on Thursday. Erdoğan and his delegation will later meet American businessmen at the US Chamber of Commerce and attend a dinner at the White House.
The prime minister started his trip in the US with a groundbreaking ceremony for the Turkish-American Culture and Civilization Center in Maryland on Wednesday.
Speaking at the ceremony, Erdoğan said that the multifunctional center would be an honor of the Turkish nation. "This monument will be a symbol of our understanding of culture and civilization," Erdoğan added.
The prime minister thanked everyone who launched the project for the center and those who purchased the land and developed the project.
"I believe that this center would be a place visited by not only those who have come from Turkey but also friends living in the United States," Erdoğan stressed.
Erdoğan also said that the center would be a matter of pride for Turkey, an important actor of the Alliance of Civilizations project, thanking the US administration, the Turkish Religious Affairs Directorate, officials of the Turkish Foreign Ministry and all philanthropists for supporting the project.
Erdoğan noted that the center will be a good way to show how wrong Islamophobia is by giving messages of Islam's brotherhood and tolerance, adding that once the center is completed, the state of Maryland will experience a different richness.
"With its multifunctional character, the center will be a source of pride for the Turkish nation," Erdoğan added.
Erdoğan also said the Turkish American Culture and Civilization Center would be an expression of coexistence based on love and tolerance.
On Friday Erdoğan is set to deliver a speech at the Brookings Institution, an American think tank, and attend a conference organized by the Foundation for Political, Economic and Social Research (SETA). Later, he will attend a reception hosted by the Turkish Embassy in Washington.
As part of his seven-day visit to the US, Erdoğan is also expected to visit world technology capital Silicon Valley as well as meet representatives from Muslim and Turkish communities.
Erdoğan became the first Turkish leader to be greeted by a US military ceremony at an airport in Washington in a sign of strong ties with the United States.
Erdoğan's spouse, Emine Erdoğan, and Foreign Minister Ahmet Davutoğlu also accompanied the prime minister during his trip.
In addition to Davutoğlu, Deputy Prime Minister Bülent Arınç, Economy Minister Zafer Çağlayan, European Union Minister Egemen Bağış, Defense Minister İsmet Yılmaz, Energy and Natural Resources Minister Taner Yıldız and a number of businesspeople also accompanied Erdoğan during his trip to the US.