Many gay activists are frustrated Obama has not moved more quickly to carry out election promises, such as repealing the Defense of Marriage Act, which bars the federal government from forcing states to recognise gay marriage.
Activists plan to march in Washington on Sunday to urge action on these issues.
At the dinner, Obama acknowledged that work on those issues was "taking longer than you'd like" as the push to overhaul healthcare and dealing with the economic crisis dominate his domestic agenda.
But he promised "unwavering" support for broadening the rights of gays and lesbians and said he would not allow the issue to be sidetracked.
"Do not doubt the direction we are heading and the destination we will reach," Obama said, comparing the push for gay rights to the struggles in the 1960s to end discrimination against blacks.
"My expectation is that when you look back on these years, you will see a time when we put a stop to discrimination against gays and lesbians, whether in the office or on the battlefield."
Obama touted his decision to extend some benefits to partners of gay federal employees and said he hopes to soon sign a bill that would broaden the definition of hate crimes to include attacks on people because of their sexual orientation.
The House of Representatives passed the bill last week and the Senate is expected to act soon.
Obama last week nominated an openly gay lawyer, David Huebner, to serve as his ambassador to New Zealand and Samoa.