Moscow has denied any interference, and Mr. Trump says his campaign did not collude with Russia.

President Donald Trump's eldest son eagerly agreed to meet with a woman he was told was a Russian government lawyer who might have information incriminating Democratic rival Hillary Clinton as part of Russian government support for his father, according to an email chain released on Tuesday.

The email chain was between Donald Trump Jr., who posted it on Twitter, and Rob Goldstone, an intermediary who helped to arrange the eventual meeting with the lawyer. It could provide ammunition for investigators who are probing whether there was collusion between the Kremlin and Trumps presidential campaign.

“The Crown prosecutor of Russia ... offered to provide the Trump campaign with some official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to your father,” said the June 3, 2016, email to Donald Trump Jr. from publicist Rob Goldstone.

“This is obviously very high level and sensitive information but is part of Russia and its government's support for Mr. Trump,” according to the email posted by Mr. Trump Jr. on Twitter.

“If it's what you say I love it,” Mr. Trump Jr. replied in part.

Here's my statement and the full email chain pic.twitter.com/x050r5n5LQ — Donald Trump Jr. (@DonaldJTrumpJr) July 11, 2017 Here is page 4 (which did not post due to space constraints). pic.twitter.com/z1Xi4nr2gq — Donald Trump Jr. (@DonaldJTrumpJr) July 11, 2017

The email exchange includes at least one error. Russia, which ceased to be a monarchy with the Russian Revolution, does not have a “crown prosecutor” but rather a prosecutor general. A spokesman for the prosecutor general declined to comment immediately.

Financial markets appeared to have been jarred by the sudden disclosure from Mr. Trump Jr.

Following his tweets, the S&P 500 Index slid by about 0.6% in the span of about 20 minutes, although it has since retraced about half that move. The dollar index, the broadest measure of the U.S. currencys strength, weakened by about 0.16%. U.S. 10-year Treasury futures, meanwhile, gained ground.

Legal experts are divided on whether Mr. Trump Jr.'s participation in the meeting with the Russian lawyer could lead to criminal liability.

Collusion in and of itself is not a crime. But if the younger Mr. Trump conspired or aided and abetted a criminal action, such as hacking into American computer networks, that could be grounds for criminal charges. Several lawyers also said the meeting could run afoul of federal election laws barring campaigns from accepting gifts or things of value from foreign nationals.

The emails do not at first glance appear to provide evidence of illegal activity, and Mr. Trump Jr. has said a meeting he later had with a Russian lawyer arranged via Goldstone primarily involved discussion of U.S. sanctions.

However, Goldstone's statement that the promise of incriminating information on Democratic presidential candidate Clinton was “part of Russia and its governments support for Mr. Trump” provides new ammunition for federal and congressional investigators who are probing Russia's alleged interference in the 2016 U.S. presidential campaign in which Mr. Trump beat Ms. Clinton.

Moscow has denied any interference, and Mr. Trump says his campaign did not collude with Russia.