Aiming to steer more federal aid to the smallest and most vulnerable businesses, the Biden administration is altering the Paycheck Protection Program’s rules, increasing the amount sole proprietors are eligible to receive and imposing a 14-day freeze on loans to companies with 20 or more employees.

The freeze will take effect on Wednesday, the Small Business Administration planned to announce on Monday. Also, President Biden is expected to speak shortly after noon on Monday to make an announcement about small businesses.

In December’s economic relief package, Congress allocated $284 billion to restart the aid program. Banks and other financiers, which make the government-backed loans, have disbursed $134 billion to 1.8 million businesses since lending resumed last month. The money is intended to be forgiven if recipients comply with the program’s rules.

Companies with up to 500 workers are generally eligible for the loans, although second-draw loans — available to those whose sales dropped 25 percent or more in at least one quarter since the coronavirus pandemic began — are limited to companies with 300 or fewer employees. The 14-day moratorium is intended to focus lenders’ attention on the tiniest businesses, according to administration officials, who spoke to reporters at a news briefing on Sunday on the condition that they not be named.

Most small businesses are solo ventures, employing just the owner. For such companies, including sole proprietorships and independent contractors, one major impediment to getting relief money was a program rule that based their loan size on the annual profit they reported on their taxes. That made unprofitable businesses ineligible for aid, and left thousands of applicants with tiny loans — some as small as $1.

The new formula, which Small Business Administration officials said would be released soon, will focus instead on gross income. That calculation, which is done before many expenses are deducted, will let unprofitable businesses qualify for loans.

The agency is also changing several other program rules to expand eligibility. Those with recent felony convictions not tied to fraud will now be able to apply, as will those who are delinquent or in default on federal student loan debt. The agency also updated its guidance to clarify that business owners who are not United States citizens but lawful residents are eligible for loans.

Treasury Secretary Janet Yellen on the road to recovery:

On top of the $1.9 trillion economic aid plan that is working its way through Congress, the White House is raising the prospect of another big spending package focused on infrastructure. Although the economy is recovering faster than expected, it remains fragile and uneven. Navigating this path is Janet Yellen, the former Federal Reserve chair who took over as Treasury secretary last month.

Treasury Secretary Janet Yellen opened the DealBook DC Policy Project on Monday, moderated by The New York Times’s Andrew Ross Sorkin, about the prospects for a post-pandemic recovery.

Highlights from the discussion:

• “We need to make sure that those who have been most affected aren’t permanently scarred by this crisis,” Ms. Yellen said. “There are a lot of different metrics we can use to judge success,” she said. “Success, to me, would be if we could get back to pre-pandemic levels of unemployment, and see the re-employment of those who have lost jobs in the service sector particularly.”

• “Of course, a key job for a Treasury secretary is to make sure our country is on a sound fiscal course,” she said. “If you don’t spend what is necessary to get the economy quickly back on track, that has a fiscal cost as well.” Although U.S. debt levels are much higher than they were during the 2008 financial crisis, because of lower interest rates, the share of interest payments as a share of G.D.P. today is roughly the same, she noted. “I think we have more fiscal space than we used to because of the interest rate environment, and I think we should consider using it.”