WASHINGTON (AP) — A leading Republican senator is calling for immediate action to stabilize shaky health insurance markets around the country, amid concerns that the GOP will get blamed if constituents' lives are disrupted.

Sen. Lamar Alexander of Tennessee called on the Trump administration Thursday to guarantee payment of billions of dollars in disputed "cost-sharing" subsidies at least through next year, and probably in 2019 as well.

The federal money allows insurers to reduce deductibles and copayments for people with modest incomes buying plans through HealthCare.gov and state-run markets...