WASHINGTON — President Biden unveiled a $2.3 trillion infrastructure plan centered on fixing roads and bridges, expanding broadband internet access and boosting funding for research and development, plus higher corporate taxes to pay for the package. "It's not a plan that tinkers around the edges," Mr. Biden said during a speech in Pittsburgh, where he kicked off his presidential campaign. "It's a once-in-a-generation investment in America." The Democratic president cast his plan as a fundamental shift in economic thought away from the small-government, tax-cutting approach embraced decades ago under Ronald Reagan, a Republican. "Here's the truth: We all will do better when we all do well," Mr. Biden said, arguing that the pandemic had exposed longstanding inequalities in the country. "It's time to build our economy from the bottom up and from the middle up, not the top down." He said his plan isn't an attack on wealthy Americans. "This is not to target those who've made it, not to seek retribution," he said. "This is about opening opportunities for everybody else." The president's advisers say the Covid-19 pandemic has helped change American attitudes about the role government should play in their lives, making political space for unprecedented investments that could reshape the country. The measure, which comes after Mr. Biden signed a $1.9 trillion coronavirus relief bill into law, is the first of a two-part economic plan that he hopes to move through Congress in coming months. A second plan focused on child care, healthcare and education will be released in April. Combined, Mr. Biden's economic proposals are expected to cost between $3 trillion and $4 trillion over a decade, according to people involved in the discussions. Mr. Biden's infrastructure proposal faces hurdles, including GOP opposition to significant tax increases, disagreements among Democrats about how to pay for the package and progressives' concerns that it isn't ambitious enough. The infrastructure plan would cost roughly $2.3 trillion over eight years and be paid for over 15 years by raising the corporate tax rate to 28% from 21% and increasing taxes on companies' foreign earnings. The tax changes would revamp or replace much of the international tax structure congressional Republicans established four years ago in the law signed by then-President Donald Trump. Mr. Biden's proposal includes $621 billion to modernize transportation infrastructure, $400 billion to help care for the aging and those with disabilities, $300 billion to boost the manufacturing industry, $213 billion on retrofitting and building affordable housing and $100 billion to expand broadband access, among other investments.