Vladimir Putin wrote the "basic content" of an op-ed warning against US military intervention in Syria that appeared under his name in the New York Times, although his assistants then fleshed out the text, the Russian president's spokesman has told the Guardian.

The article was offered to the Times on Wednesday by the public relations firm Ketchum, which works on behalf of Russian interests in the US and elsewhere. The paper said it required "little editing" and was published soon after it was received.

Putin's spokesman Dmitry Peskov said the article was all Putin's idea. "The basic content was written by [Putin], then his assistants worked out the text," Peskov said.

The op-ed argued against US military intervention in Syria, and derided as "extremely dangerous" Barack Obama's recent comment that America's ability to act against injustice around the world was what makes it "exceptional".

It was published before a meeting on Thursday between secretary of state John Kerry and foreign minister Sergei Lavrov to discuss a Russian plan to place the Syrian government's chemical weapons under international control.

The Times editorial page editor, Andrew Rosenthal, confirmed on Thursday that he had been approached by an American public relations firm – he did not name Ketchum – that represents Putin, pitching the piece. A spokesman for Putin had also contacted the NYT's Moscow bureau to float the idea, Rosenthal said.

"I thought it was well-written, well-argued," Rosenthal told the NYT's public editor Margaret Sullivan. "I don't agree with many of the points in it, but that is irrelevant."

"Syria is a huge story, and Putin is a central figure in it," Rosenthal added.

Eileen Murphy, a spokeswoman for the New York Times, confirmed that it was Ketchum who approached the newspaper. A spokeswoman for Ketchum said she could not comment on the op-ed but that the company would be providing a written statement later.

According to a Department of Justice filing published by ProPublica, Ketchum was under contract with the Russian Federation to promote "Russia as a place favorable for foreign investments". The contract was extended late last year, and ProPublica reported that the PR firm received $1.9m from Russia in the first half of 2013.

"The opinion piece was written by President Putin and submitted to the New York Times on his behalf by Ketchum for their consideration," Ketchum said in a statement to the Guardian.

Peskov's suggestion that the president decided to write the piece only two days ago suggested that he may have been provoked by Obama's statements. In a speech at the White House on Tuesday, Obama said the United States would work with Russia and other countries to force Syria to hand over its chemical weapons, but also that the US military would remain in place in the region in case a strike was needed to protect America's security.

Putin's comments caused consternation among politicians and commentators in the United States. Senator Robert Menendez, the chairman of the foreign relations committee, said on CNN he "almost wanted to vomit" when he read the op-ed at dinner on Wednesday. The article "really raises the questions of how serious this Russian proposal is," Menendez said.

"We are pleased that there are both positive reactions and criticism," Peskov said about the article's reception in the United States. "That means that no one was left indifferent."

In his only previous op-ed in the New York Times in 1999, Putin justified the bloody military action that eventually re-established Russian control of the breakaway province of Chechnya. The tone of this first piece, in which Putin asked readers to picture a bombing on Manhattan's west side and armed militias in Montana and Idaho, was in some ways reminiscent of Obama's comments on Tuesday about the civilian casualties of the chemical attack outside Damascus.

"Sadly, decisive armed intervention was the only way to prevent further casualties both within and far outside the borders of Chechnya, further suffering by so many people enslaved by terrorists," Putin wrote.

Putin unveiled a new foreign policy document in February that named soft power and economic diplomacy the new top priorities of Russia's relations with the world. The country would "develop its own effective means of information influence on public opinion abroad," the document stated.