European stocks are likely to drift lower Wednesday following a downbeat session in Asia in which investors appeared to focus on global oil and currency markets ahead of this week's OPEC meeting in Vienna and minutes from the Federal Reserve's last rate meeting later today.

Britain's FTSE 100 is set for a modest 5 point gain, however, according to financial bookmakers IG, although much of the market's attention will centre on the developing security situation in the U.K., where Prime Minister Theresa May increased the terrorist threat level to "critical" last night and warned that a new attack could be imminent.

The pound was marked little change from Tuesday's close at 1.2971 as trading began in Europe, with investors yet to factor-in changes to the country's terror threat level, which could mean as many as 5,000 troops deployed at public events over the coming weeks.

The U.S. dollar notched a notable mini-rally overnight, with the dollar index rising to 97.41, as investors reacted to the release of President Donald Trump's budget plans.

The release of minutes from the Fed's two-day policy meeting earlier this month in which Janet Yellen and colleagues made no changes to the central bank's interest rate projections but indicated caution with respect to the slowing U.S. economy will dictate the dollar's path for most of the session.

Overnight in Asia, regional shares fell and the Australian dollar slumped after Moody's Investors Service lowered its sovereign credit rating on China to A1 -- the first reduction since 1989 -- amid concern for rising debt levels and a slowing economy.

The MSCI Asia ex-Japan index was marked 0.2% lower by 06:30 BST while the Nikkei 225 ended the session with a 0.7% gain to close at 19,742.98 points.

Global oil prices were firmer overnight, although not spectacularly so, with investors cementing bets that OPEC minister meeting in Vienna Thursday will announce an agreement to extend production cuts throughout 2017 and into the first quarter of next year.

WTI futures for July delivery were marked 10 cents per barrel higher, or 0.20%, at $51.57 in early European trading while Brent contracts for the same month were seen 0.22% from their Tuesday close in New York at $54.27 per barrel.

Wall Street looks set for a modest slip at the start of trading later today, according to early prices from U.S. equity futures, with the Dow Jones Industrial Average likely to fall around 10 points at the opening bell, or 0.05%, with similar percentage declines anticipated for the S&P 500 and the Nasdaq.