US President Barack has announced the ban on openly gay people serving in US military is to end on September 20.
His certification on Friday of the repeal of the "don't ask, don't tell" (DADT) law comes seven months after it was overturned in the US Congress.
The Pentagon had asked for time following the repeal to prepare troops for the arrival of openly gay comrades.
Mr Obama's move affirmed the Pentagon had declared it was ready to accept openly gay troops.
'Served in silence'
"I have always been confident that our dedicated men and women in uniform would transition to a new policy in an orderly manner that preserves unit cohesion, recruitment, retention and military effectiveness," Mr Obama said in a statement.
"As of 20 September, service members will no longer be forced to hide who they are in order to serve our country. Our military will no longer be deprived of the talents and skills of patriotic Americans just because they happen to be gay or lesbian."
With the certification, Mr Obama signalled that he, Defence Secretary Leon Panetta and Joint Chiefs of Staff Admiral Mike Mullen have officially confirmed that the military is prepared, following extensive training and preparation, to implement December's repeal of the law.
"This Pentagon certification received by the White House this afternoon is welcomed by gay and lesbian service members who have had to serve their country in silence for far too long," Aubrey Sarvis, an Army veteran and executive director of the Servicemembers Legal Defence Network, which advocated the law's repeal for 17 years.
"The troops and their commanders are ready."
Under the US policy of DADT, established in 1993, gay people could serve in the military but could not acknowledge their orientation. The military was forbidden to inquire but was permitted to expel service members found to be gay.
More than 13,000 service members have been dismissed under the policy.
The end of DADT fulfils a campaign pledge made in 2008 by President Barack Obama, who signed it into law in December.
Britain, Israel and dozens of other countries allow gay personnel to serve openly.