Sen. Charles Schumer wants the federal Drug Enforcement Administration to prevent online sales of synthetic marijuana by blocking credit card companies from allowing transactions, he said Sunday.

Many websites selling the drug are based in China, making it difficult to curb sales, Schumer said. One solution, he said, would be to forbid credit card companies from allowing the sale of the drug, also known as K2 or Spice.

"These drugs are more dangerous and can have worse side effects than marijuana -- and they're becoming even more popular than marijuana because they are so available," Schumer said, speaking at a news conference at his Manhattan office. "An all-too-high percentage of these illegal drugs are available on the Internet. They're available to bodegas that want to sell them directly to people. They're available to street gangs, you can just go online and buy them. And they're available to drug rings that buy the precursor chemicals and then make them into drugs and sell them on the streets."

The DEA, Schumer added, should also publish any new information on new brands of synthetic marijuana found online.

Schumer, holding up a phone with a website purporting to sell synthetic marijuana to anyone willing to pay with a Visa credit card or an e-check, said the DEA should force the credit card companies to block the sale before the drugs are shipped.

"By cutting off credit card access to these Chinese companies that sell illegal drugs, we're choking these websites. We're depriving them of oxygen and they will shut down," Schumer said. "The DEA has the power to do it, they simply don't have the resources.

"The credit card companies, we have clout over," he added.

Last week, Mayor Bill de Blasio said the city has been organizing a multiagency attack against K2, leading to 10 men being charged in a synthetic marijuana drug ring, as well as fewer emergency room visits.

The drugs are popularly sold in bodegas for about $5 per bag, authorities have said.

There were more than 3,000 synthetic marijuana-related emergency department visits this year, according to the mayor's office.