WASHINGTON (REUTERS) - The US Senate narrowly confirmed President Joe Biden's nominee, Colin Kahl, to be the Department of Defence's top policy adviser on Tuesday (April 27), ending a bitter confirmation battle with Republicans.

The Senate voted 49 to 45 to confirm Kahl, 49, who served as national security adviser to Biden when the Democrat was vice-president, to be undersecretary of defence for policy. The position is the No. 3 civilian job at the Pentagon.

With the Senate divided 50-50 between the Democratic and Republican caucuses, there have been many mostly partisan votes over Biden's nominees for top administration positions.

Kahl became a prime target of Republicans aiming to torpedo some Biden picks over their activity on social media. Critics accused him of making comments on Twitter that were too partisan for him to serve effectively or of releasing classified information on social media, which he denied.

Democrats have rejected such concerns, noting Republicans' loyalty to former president Donald Trump, who frequently used his Twitter feed to insult political opponents.

The Senate Armed Services Committee vote on Kahl's nomination was a tie, forcing Vice-President Kamala Harris to come to the Senate last week to break a tie during a procedural vote, her first tie-breaking vote for a Biden nominee.