More than two-thirds back diplomatic negotiations with Iran over its nuclear program.
His absence from the public eye for nearly two weeks led to speculation about his health.
“We have to negotiate in the end,” Kerry told CBS News.
"I think it's interesting that we've had so much talk about process," Sen. Roger Wicker said.
"I think it's appalling to interfere in a negotiation like this," Rep. Adam Schiff said.
Kerry said the letter from 47 GOP senators presents "false information."
The U.S. and its allies are ratcheting up their military presence in the Persian Gulf.
Officials are bringing home other health workers who may be at risk for the disease.
America has given the opposition a total of $400 million in assistance.
But Sen. Ron Johnson (R-Wis.) defended the "content" of the letter.
Romney urges Obama to "walk away" from his "flimsy nuclear agreement."
Netanyahu's party released a campaign ad with footage of the speech.
The letter reportedly came up in discussions on Sunday and Monday.
Obama's two recent trips abroad sum up the hope and disappointments of his foreign policy.
The White House leveled new sanctions on Venezuela last week.
“These negotiations have gone in a dramatically bad direction,” Sen. Roy Blunt said.
The former governor said foreign policy should be conducted by the president.
A top Obama aide warned that legislation could set a "potentially damaging precedent."
Quiz highlights quotations about Iran nuclear talks.
Obama appealed directly to Chinese leader Xi Jinping to stop a pending law.
Maybe it makes sense to look at his record.
The program allows citizens from 38 countries to visit the U.S. without a visa.
The department says Clinton used her own phone while serving as secretary.
A petition tells Clinton to avoid a "conflict of interest" on the pipeline.