After the announcement, shares of United Technologies fell more than 2 percent in morning trading, while Honeywell's shares jumped more than 2 percent.
United Tech rejected Honeywell's offer last week, saying a merger would be "irresponsible" toward its shareholders. The two companies were also in talks in May 2011 and April 2015, according to Honeywell's statement.
"From both an industrial logic and shareholder value perspective, Honeywell and United Technologies are a great match and that is why the two companies have been talking about a combination for more than 15 years," Honeywell Chairman and CEO Dave Cote said in a statement. "We made a full and fair offer that would have greatly benefited both sets of shareowners."
[Honeywell CEO David Cote will be on CNBC's "Mad Money" on Wednesday at 6 p.m. ET]
United Technologies did not immediately return CNBC's request for comment.
Though the combination of the engineering and manufacturing companies was expected to achieve cost savings, United Technologies predicted antitrust roadblocks to the union, according to Honeywell, which will have an investor day Wednesday.
Shares of United Technologies are down about 20 percent over the past year, while shares of Honeywell are down about 1 percent.
—Reporting by CNBC's David Faber. Reuters contributed to this report.