President Joe Biden on Thursday predicted that his fellow Democrats could win two more U.S. Senate seats in November's midterms, strengthening the party's majority to pass his agenda despite sagging approval ratings.

Speaking at a political fundraiser in Portland, Biden said he needed to make the case around the country about what his administration had accomplished and that was a reason he was traveling more.

"I'm determined to make sure we keep the House and the Senate," Biden told the donors. He offered no prediction for the party's prospects in the House.

High inflation and the ongoing pandemic have contributed to low poll numbers for Biden and sparked concerns Democrats may lose control of the House of Representatives and the Senate to Republicans after the November election.

Earlier on Thursday, Biden touted his administration's progress on infrastructure, including new spending made possible by the passage of the roughly $1 trillion infrastructure law that includes investments in highways and broadband. The bill allocates $1.2 billion for Oregon and $8.6 billion for the state of Washington.

Biden visited Portland's airport to talk about investing in a runway that can withstand earthquakes. He will spend Thursday night and Friday in Seattle, where he will observe Earth Day and talk about his administration's plans to tame inflation.

"We're here today to talk about investments we're making to modernize this airport," Biden said in his earlier address. "So through the bipartisan infrastructure law, we're investing $25 billion to upgrade and modernize American airports."

White House officials have said in recent weeks that they hope to shift their outreach strategy to voters by visiting more states to talk about the administration's accomplishments rather than describing the need for legislation that remains stalled.

Biden's public approval rating stands at 43%, according to a two-day Reuters/Ipsos opinion poll completed on Tuesday. The two-day national poll found 51% of Americans disapprove of Biden's job performance as the country struggles with high inflation and Russia's invasion of Ukraine.

That compares with approval ratings hovering above 50% at the start of his term.