The new bid amounts to $127.50 per NXP share and aims to satisfy NXP shareholders who had expressed concern the Qualcomm bid was too low.

By moving closer to a tie-up with NXP, Qualcomm could make it more difficult for Broadcom, which is pressing ahead with a record $121 billion offer despite opposition from Qualcomm's board.

Qualcomm called the offer an "amended definitive agreement" with NXP which includes the support of hedge fund shareholders of the Dutch firm. With NXP debt, the deal's value is over $50 billion.

Adding NXP would give a broader array of products including sensors and microprocessors for connected "internet of things" devices to Qualcomm, which is the dominant maker of chips for smartphones.

"NXP is a highly strategic and attractive acquisition for Qualcomm that enhances the value of our leading 5G technologies," said Qualcomm chairman Paul Jacobs, referring to the fifth generation of wireless technology which is being deployed around the world.

"We also believe the revised agreement provides certainty for both Qualcomm and NXP stockholders."

Qualcomm's move comes after it rejected for a second time last week the Broadcom bid, with the Singapore-based firm indicating it will press its case to the Qualcomm shareholders' annual meeting next month.

In rebuffing Broadcom, Qualcomm executives have said the offer undervalues the US firm in light of its growth potential for 5G products and failed to consider the value of NXP. It also said a Broadcom-Qualcomm tie-up could face a difficult regulatory path with antitrust authorities.

Qualcomm has faced antitrust probes in several countries over its dominance of the mobile chip market.

According to Qualcomm, the acquisition of NXP has received antitrust clearance from eight of the nine required government regulatory bodies around the world, with the matter still pending in China.

Qualcomm said it was optimistic it will receive clearance "in the near term" from Chinese authorities.

Responding to the news, Broadcom said the new offer effectively transfers $6.2 billion of Qualcomm value to the Dutch firm.

"Broadcom believes the price increase demonstrates the Qualcomm board's disregard for its fiduciary duty to maximize value for Qualcomm stockholders," the firm said in a statement.

"In light of Qualcomm's decision to transfer value from its own stockholders to NXP stockholders, Broadcom is evaluating its options."

Qualcomm said it would proceed with the deal if it is approved by 70 percent of NXP shareholders by March 5 -- the day before the Qualcomm annual shareholders' meeting.