House Democratic leader Nancy Pelosi said Thursday the nuclear deal negotiated by the United States, Iran and Western powers "will have my strong support."

"I'm very optimistic about our ability to support the president" on the agreement, Pelosi told reporters at her weekly news conference.

The Obama administration has launched a full-court press to win over skeptical Democrats in Congress, and Pelosi's support is a key gain. The historic agreement would curb Tehran's nuclear program in exchange for billions of dollars in sanctions relief.

By law, the administration must submit the deal to Congress, which has 60 days to review the pact and vote to approve, disapprove or remain silent.

Vice President Joe Biden met with House Democrats on Wednesday to brief them on the deal. The vice president was returning to Capitol Hill on Thursday for a session with members of the Senate Foreign Relations Committee.

Secretary of State John Kerry, Energy Secretary Ernest Moniz and Treasury Secretary Jack Lew are scheduled to testify before the panel next week.