The US House of Representatives Foreign Affairs Committee has launched an investigation into US President Donald Trump's blocking of funds for the World Health Organization.
It gave the US State Department a week to provide information about the decision as the world faces the coronavirus pandemic.
Democratic Representative Eliot Engel, the committee's chairman, said the UN health agency is "imperfect" and that he would support reforms, "but, certainly, cutting the WHO's funding while the world confronts the Covid-19 tragedy is not the answer", he said in a letter to Secretary of State Mike Pompeo.
Mr Trump suspended US contributions to the WHO on 14 April, accusing it of being "China-centric" and promoting China's "disinformation" about the coronavirus outbreak and saying his administration would launch a review of the organisation.
WHO officials have denied the claims and China insists it has been transparent and open. The US is the WHO's biggest donor.
In the letter, Mr Engel asked the State Department to provide 11 sets of documents or other information related to the decision to withhold funding no later than 5pm on 4 May.
If it does not do so, Mr Engel said the committee would consider all measures at its disposal. A spokesman declined to provide specifics.
Mr Engel has the authority as a committee chairman to issue subpoenas to federal agencies.
The State Department did not immediately respond to a request for comment.
Mr Trump's 14 April decision prompted immediate criticism from US allies abroad, and within the US, from health experts and Democrats.
Some Democrats accused the Republican president of using the WHO and China as scapegoats to distract from what they view as Mr Trump's mishandling of a pandemic that has killed nearly 55,000 Americans and cratered the US economy.
But Mr Trump's fellow Republicans have largely backed the president, praising his handling of the health crisis and calling on WHO Director General Tedros Adhanom Ghebreyesus to resign.
Meanwhile, New York Governor Andrew Cuomo said his stay-at-home order will likely be extended beyond 15 May in many parts of the state, but that restrictions could be relaxed in some regions if they have sufficient hospital capacity and meet other criteria.
Mr Cuomo also told a daily briefing that New York has now tested 7,500 people for antibodies against Covid-19 and that 14.9% tested positive, indicating they were infected and survived.
The infection rate was up from 13.9% when the initial results from 3,000 people were disclosed last week.
Mr Cuomo said the larger sample added to his belief that the fatality rate from Covid-19, calculated by dividing the number of deaths by the infection rate implied by the antibody testing, may be lower than some experts had feared.
"The death rate is much, much lower because it changes the denominator," Mr Cuomo said.
Meanwhile, other US states from Minnesota to Mississippi are preparing to join other states that have eased coronavirus restrictions to try to revive their battered economies, although some business owners have voiced reluctance in the face of health warnings.
Colorado, Montana and Tennessee are also set to allow some businesses deemed non-essential to reopen after being shut for weeks even as health experts advocated for more diagnostic testing to ensure safety.
Georgia, Oklahoma, Alaska and South Carolina previously restarted their economies following weeks of mandatory lockdowns that have thrown millions of American workers out of their jobs.
The number of known US infections has kept climbing, topping 970,000 as the number of lives lost to Covid-19 surpassed 54,800.
Public health authorities warned that increasing human interactions and economic activity may spark a new surge of infections just as social-distancing measures appear to be bringing coronavirus outbreaks under control.