US Democratic presidential candidate and US Senator Barack Obama, (D-IL), waits to speak in Billings, Montana May 19, 2008. (Xinhua/Reuters Photo)

Sunday's Democratic presidential primary in US territory of Puerto Rico was a clean sweep for Senator Hillary Clinton, who vowed to keep running against all odds.

However, the real news of the day is not Clinton's largely symbolic victory, but her rival Senator Barack Obama's preparations to announce he wins the party's nomination, which many believe will come within days.

It's a simple question of math. A candidate needs at least 2,118 national convention delegates to get the Democratic Party's presidential nomination this year.

After the Puerto Rico primary, in comparison to Clinton's 1,915 delegates under her column, Obama now has some 2,070 delegates and is only less than 50 delegates short to secure the nomination.

There are only two primaries left, which are to held on June 3, and there only 31 pledged delegates left for grabs.

Apparently it's impossible for Clinton to catch up with Obama in the delegate tally as the party is wrapping up the primary election cycle.