Washington, Jul 25 (IANS): Senator John McCain, diagnosed with an aggressive form of brain cancer, will return to the Senate on Tuesday to cast a critical vote on health care legislation, the media reported.

McCain's office announced on Monday night that he would return Tuesday -- a surprise to most in Washington who expected him to miss the crucial vote and return to Washington at a later date, reports CNN.

McCain is expected to get Republican leadership one vote closer to beginning debate on health care legislation, which is on the verge of collapsing.

"Senator McCain looks forward to returning to the US Senate tomorrow (Tuesday) to continue working on important legislation, including health care reform, the National Defence Authorization Act, and new sanctions on Russia, Iran and North Korea," his office said in a statement.

The Arizona Republican underwent brain surgery earlier this month and announced last week he has been diagnosed with brain cancer.

But McCain's return hardly guarantees leadership will be able to advance a health care bill now, CNN reported.

It helps, but Senate Majority Leader Mitch McConnell still needs at least 50 votes to start debate on overhauling Obamacare, and can only lose two votes from his 52-member conference.