An Apple spokesman and a Qualcomm spokeswoman said no further details of the settlement were immediately available. Qualcomm said more information might be disclosed when it releases financial results on May 1.

Apple may have been under pressure to strike a deal with Qualcomm because one of its current chip suppliers, Intel, said late Tuesday that it planned to stop selling wireless modem chips for smartphones — including the chips with faster 5G connectivity that Apple had been expected to use next year. Qualcomm is already selling chips that can support 5G wireless technology to Apple’s rivals, such as Samsung Electronics. Samsung is expected to have 5G handsets using Qualcomm chips this year.

An Intel spokesman declined to comment further.

The battle between the two companies began in January 2017 when the F.T.C. filed a case against Qualcomm that partly leaned on Apple’s contentions. The F.T.C. alleged that Qualcomm was able to charge unfairly large royalties because handset makers had no leverage to negotiate, especially because Qualcomm supplied two key types of chips and could cut off shipments if the buyers balked at paying royalties.

Three days after the F.T.C. filed its case, Apple separately sued Qualcomm. In its suit, Apple objected particularly to Qualcomm’s basing its royalties on a phone’s total price. That formula, Apple argued, meant that Qualcomm earned more money as handset makers added innovations like displays, touch sensors and data storage unrelated to wireless technology.

The case dragged on with four Asia-based contract manufacturers that assemble iPhones and iPads, whose suits against Qualcomm were eventually merged with Apple’s. They argued that they had collectively overpaid Qualcomm roughly $9 billion in royalties over the years — a figure that could have been tripled under antitrust laws to $27 billion. Apple also had said Qualcomm should repay $3.1 billion associated with patents whose rights Apple said have been exhausted.

Qualcomm then sought to pressure Apple to settle by filing a series of patent suits, including cases in China and Germany and through the United States International Trade Commission. It also persuaded courts in some countries to ban sales of some iPhone models, though Apple was able to keep selling its handsets with tactics that included tweaking some of its software.

Much of the world-spanning fight appeared to be coming to a head this week in the United States District Court for the Southern District of California, where a jury was selected on Monday for a trial on Apple’s lawsuit and Qualcomm’s counterclaims. Opening statements started Tuesday morning and were set to continue in the afternoon when the settlement was announced.