NEW YORK/WASHINGTON (Reuters) - U.S. drugmaker Merck & Co Inc said on Tuesday that its Chief Executive Ken Frazier plans to testify at a Senate hearing later this month examining rising prescription drug prices.

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Republican Senator Chuck Grassley, chairman of the Senate Finance Committee, and Democratic Senator Ron Wyden, ranking member of the committee, on Monday invited executives from seven pharmaceutical companies, including Merck, to testify. The others are AbbVie Inc, AstraZeneca Plc , Bristol-Myers Squibb Co, Johnson & Johnson, Pfizer Inc and Sanofi SA.

A spokesman from Senator Grassley’s office said on Monday that two of the CEOs have agreed to testify so far, but did not specify from which companies.

A Sanofi spokeswoman said the French drugmaker was reviewing Chief Executive Olivier Brandicourt’s scheduling to determine if he can attend the hearing. Britain-based AstraZeneca said it was reviewing the request and will respond to the committee.

Pfizer, Bristol-Myers, and J&J did not immediately have a statement on the invitation to testify, while AbbVie did not respond to a request for comment.

The United States, which leaves drug pricing to market competition, has higher prices than in other countries, where governments directly or indirectly control costs. That makes it by far the world’s most lucrative market for manufacturers.

Congress has been targeting the pharmaceutical industry over the rising cost of prescription drugs for U.S. consumers, particularly since Democrats took over the House of Representatives in January.

Last week, the House Oversight Committee and the Senate Finance Committee brought in patient advocates and health policy experts to discuss the burden of high drug costs on consumers.

Senators and congressmen have also written to insulin manufacturers requesting information on why its cost has skyrocketed in recent years and how much the companies profit from the life-sustaining diabetes treatment.

Drug pricing is also a top priority of the administration of President Donald Trump, who had made it a central issue of the 2016 presidential campaign.

Drugmakers have slowed and limited U.S. price increases as scrutiny on their practices has intensified over the past few years.

They nonetheless increased prices on hundreds of drugs in January, including a 6.2 percent increase on the world’s top-selling drug - AbbVie’s rheumatoid arthritis treatment Humira - and hikes on insulin prices by Sanofi and Novo Nordisk.