The tech giant had already come under fire this year from thousands of employees who signed a petition against a $10-million contract with the USA military, which was not renewed.
Meanwhile, Pichai has made repeated trips to China to discuss the project with some of the country's top Communist leaders.
The new project is said to be codenamed "Dragonfly".
Employees have demanded that the company be more transparent about its decisions, and the letter also calls the project's ethics into question.
"We urgently need more transparency, a seat at the table and a commitment to clear and open processes: Google employees need to know what we're building", states the document seen by Reuters. The company did not renew the contract with Pentagon for that project, and also laid out some ethical principles about the use of its Artificial Intelligence.
Google, which has never spoken publicly about the plans, declined to comment. But new reports say Google is building a brand new, censored search engine that will allow it to re-enter the Chinese market, where it will be actively abetting the Communist police state. He noted the company guards information on some projects where sharing too early can "cause issues".
White House lawyer Donald McGahn 'cooperating extensively' with Robert Mueller
Mueller's investigation has resulted in several guilty pleas by people once connected to the Trump campaign for lying to the FBI. Dean began his response to Trump with a zinger. "And his client is not Donald Trump; his client is the office of the president".
Kohli-Rahane salvage India from first day disaster at Trent Bridge
Anderson and Broad bowled a tad short and the ball didn't swing much in the first hour of play as India were well placed at 43-0. There was little resistance from the lower order on Sunday, with India losing their last four wickets for 22 runs in 19 balls.
Trump Cancels His Military Parade as Costs Soar
And that set off a volley of tweets and accusations between the president and the mayor of the nation's capital. Trump blaming the cost on local DC politicians, who "wanted a number so ridiculously high that I cancelled it".
Google's claim of being free of political bias in its downgrading of websites is a lie that has been fully exposed by its increasingly aggressive efforts to decrease or block readers' access to sites that promote oppositional information and viewpoints.
The United States is locked in a bitter dispute with China over its technology sector, with Washington seeking to block the growth of smart phone makers Huawei and ZTE, while promoting the expansion of USA technology firms such as Google in the Chinese market. This, along with all the censorship laws, forced Google to withdraw from China after 4 years of existence. While it still maintains offices in the country, it has been seeking to increase its presence.
The search engine, which would be app-based, would remove items that contain certain words or phrases and would apply to image search, suggested search features and automatic spell check.
When you type a query into Google's search engine, there's the Search button, which leads you to a snippet of information and various link suggestions, as well as a more playful option ("I'm feeling lucky"), a click that will send the user directly to a webpage of Google's choosing.
Regardless of the outcome of the talks, it is clear that Google has no objection to state censorship and is willing to collaborate with any government, whether Trump's America or Xi's China, to implement it.